#underlust3r

In Undertale, Mettaton's "MTT Resort" is a prominent location associated with Hotland. It consists of a Restaraunt, a Hotel, and a Fast Food Vendor (worked by Burgerpants).

In Underlust3r, I think it would be Mettaton's main studio where he films his Quiz show (instead of the restaurant), with a huge Library (instead of a Fast Food Vendor), and small private reading rooms that are converted to Hotel rooms in a pinch.

Underlust Tonton values and yearns to share knowledge, not necessarily for fame (and especially not for attention after his assault). While I think he would reluctantly use his resources for public good under extenuating circumstances, I think he would largely be trying to cultivate education and literacy. His Library may even double as a bookstore and movie rental service solely as a means of income (and I lowkey suspect Tonton is salty that he makes so much money that way).

Mettaton of course deserves his own post given how prominently he features in Underlust Canon, but I wanted to establish some context for these Underlust3r changes.

Vendors

Bratty and Catty

Bratty is an Alligator monster and Catty is an Alley Cat monster. They canonically dumpster dive and sell any "really good garbage" they can find.

In Underlust3r, this is largely the same, except they often scrounge up old human porno magazines, sex toys (which they only consider 'good' if they can clean them -- Alphys lectured them for several hours about that), and leftover food from the Cooking Show specials. They used to take candid photos of Mettaton to auction off, but they stopped doing that. No they aren't telling you why, piss off. Wanna hear how many burgers that librarian can fit in his butt? It's, like, more than the movie shows~

Burgerpants

Burgerpants as an Underlust character is mentioned in a few disparate tumblr posts:

January 20th, 2017 <https://www.tumblr.com/nsfwshamecave/156133593751/whats-burgerpants-like-in-underlust> where it's revealed he wants to be a porn star but only got one gig in a food fetish film where he stuck burgers in his pants.

January 20th, 2017 <https://www.tumblr.com/nsfwshamecave/156138729581/burgerpants-how-many-burgers-can-you-fit-up-your> where it is revealed he stuck 37 burgers up his ass and would not recommend it to anyone else.

January 20th 2017 <https://www.tumblr.com/nsfwshamecave/156134846426/so-if-bp-got-into-weird-ass-food-porn-and-ncg> where it's canonized that BP and Nicecream Guy will collab on weird food porn together.

I think in Underlust3r, Burgerpants is a librarian in Mettaton's Library since he can't get any jobs in porn and he needs a steady job to pay the bills. He thinks Mettaton is squandering his resources and good looks doing boring Quiz Shows when he could be staging amazing pornos. He thinks Mettaton is a bit of a prude and resents his exacting standards for his library. But... Mettaton is also an amazing boss who never requires overtime, pays for vacation AND sick days, and doesn't ask for anything outside of the job description.

Burgerpants wishes he would ask for something outside of the job description.

(I really wanna go more into my HC's about BP and Tonton's relationship but that is its own essay so I need to stop here.)

Other Overworld NPCs

Diamond Receptionist :: This is the pink and blue triangle-shape-combination monster that will greet you in the Resort in Undertale. In Underlust3r, I think they would still greet you, but warn you that the Resort is kind of boring. After all, it's mostly just (1) seating for the live viewing of the Quiz Show, and (2) a big library.

Hand Receptionist :: In Undertale, this monster explains how the elevator to the capital is not working and claims that rooms are running at a special rate. In Underlust3r, they explain that the elevators are busted, so Mettaton has converted some of the private reading rooms into hotel rooms. Kids stay free, and adults run 10g a night, but there is a 200g deposit for cleaning fees for adults. Their nails are long, except for the middle and ring finger nails which are filed down.

Sad Dragon :: In Undertale, this monster can't go home to the capital, so they stay at the MTT Resort. In Underlust3r, this is also true, but they are clearly more upset they won't be home in time for their anniversary dinner. (And anniversary sex.)

Shambling Mass :: This is the black thing with one eye and red bowtie, which expresses their emotions about Undertale events. In Underlust3r, they are still vocally emotional. "As a slime, I am frustrated. As a slime, I am aroused. As a slime, I am disappointed."

Business Manticore :: In Undertale, this monster comments on the state of the elevator in the MTT Resort (among other things they can explain). They can be seen with their luggage next to them, suggesting that they were prepared to leave before it stopped working. In Underlust3r, I think this would largely be the same. Their briefcase definitely has a few sex toys in it though. They are a part of the Royal Harem assigned in New Home. They explain things like how the Royal Harem is a public service to make sure everyone can have safe consensual sex with a willing partner, since LUST makes abstinance a health hazard, and that they really need to get back to work soon.

MTT Resort Janitor :: This is the monster cleaning their own slime out of the hallway in Undertale. In Underlust3r, they complain about what a mess everyone else is, and how proud they are not to be. They don't seem to realize they keep dripping on the floor too (theirs just isn't sex fluid).

Fish Receptionist :: In Undertale, this monster tells you the requirements to eat at the MTT Resort. In Underlust3r, they tell you the requirements (and code of conduct) to watch the Quiz Show live. They probably sound like they think the code of conduct is excessively restrictive.

Snowdrake's Father :: In Undertale, he says his son ran away after his mother passed away, that he is "a terrible fathah" and wants to have a better relationship with his son. In Underlust3r, he does standup comedy in between Mettaton's showtimes. He misses his sick wife. Since Snowdrake (probably) doesn't exist, he laments that he always wanted to be a father, even though he doesn't think he'd be good at it.

Charles :: A mole-in-a-hard-hat who works in the CORE. They love their job even if it isn't sexy. They always watch Mettaton's Quiz show live since they get free tickets as part of their job's perks. Even if the show isn't very sexy, Mettaton still is!

Oni :: In Undertale, this red oni is sick and tired of all the puzzles underground. In Underlust3r, he's still sick and tired of all the puzzles, but what really bothers him is all the exhibitionism. He respects Mettaton for being the one performer who doesn't add gratuitous sex appeal in every performance.

Ficus Licker :: In Undertale, this monster forgot to make a reservation and licks a ficus so it looks like it knows what it's doing. In Underlust3r, I like to think they show up to the live Quiz Show on accident thinking it was going to be a sexy burlesque show, and is too embarrassed to leave so he just sits to watch anyway.

METTATON'S ABUSERS

The two monsters that rape Mettaton after his initial debut are only featured in Papyton Comic Post #2 (Feb 6, 2016), #9 (Mar 16, 2016), #10 (Mar 23, 2016), and #11 (Apr 3, 2016).

They are drawn indistinct with minimal features, each one only showing one eye (on mirroring sides, with one having a left eye and the other a right eye), a mouth, and a distinctly lithe human-shape-like body. In posts #9-#11, they are depicted all in black with white linework, and red eyes with black irises and a white pupil. It is notable that they are shown to both bleed and cry in Red. (in post #2, they are depicted with dark grey instead of black, which makes them stand out more against the darker backgrounds of those memory shots.)

These monsters are, more likely than not, OCs made to serve the narrative purpose of abusers, as they don't strictly match any one other kind of canon monsters.

Aaron is a musclehead. His design and personality are probably not all that different, except that he is a little more aggressive with his flirting and a little too handsy.

Woshua is even more aggressive about keeping clean, and gets cranky at the mention of watersports. Instead of a toy duck on the platform in its water basin, it has a suction cup dildo. It is constantly trying to keep everyone clean even in the middle of the act. (And it is apparently very popular for it.) I have interpreted Woshua's pixel art as being a large machine or bathtub with a bobble head and clawed feet. So I think it would be very interesting if Woshua was, like the ghosts, ineligible for the LUST injections due to its body being more mechanical than biological in nature, and its dildo attachment was a change made to keep customers occupied while it cleaned.

The Moldsmal and Moldbygg in waterfall are not only more numerous (their population swelling with the migration of the ones from the Ruins), but also more aggressive and grabby. Tentacle-monster-hentai grabby.

I can see Shyren as a shy yet very talented courtisan, in the sense that she performs music beautifully but is too shy to do the sexwork. She likely only does glory holes, but nobody minds.

Mad Dummy is a cranky ass angry stoner. Hates everything so much and accuses you of being horrible to the Training Dummy.

When Mad Dummy becomes Mad MewMew, she is still pissed off because, even though she doesnt actually feel attraction or have a libido, she wants to join Undyne in doing the sex too. And while she loves her body for herself, she doesn't think it will have any use or appeal for anyone else and it makes her so frustrated! (She gets so excited when she finds out about how popular Cat Girls are!!)

Gerson sells good food and medical supplies (for aftercare) at his shop. He's the local GILF and he knows it. He might be retired from the Harem, but he can still swing if he wants to! A real Swinger in his hayday! XD He probably wears different clothes: maybe something with an open V-neck and a popped collar? or maybe one of those brightly colored suits with the poofy front piece? or maybe poofy dresshirt with a cape?

The "Echo Flower Explainer" is likely much the same, but instead of saying that explaining the Echo Flower is their purpose, I think it would be their 'fetish'.

"Loren" is the monster that usually asks if you can "eat" or "kill" a star. I think their line in Underlust3r would be: "What's a star? Can you touch it? Can you taste it? Can you fuck it? ... Are you a star?"

The "Ferry" monster is the monster that pays you 3G to transport the player across the Waterfall map, specifically from a room before the Crystal room to a room after the Wishing Room. This is activated by stepping on its face. Given that it thanks the player for stepping on its face and pays the player 3G for the privilege, this monster would likely be unchanged in function, but be a little more obviously kinky about the whole thing. The price of face-stepping would go up to 5G though.

Onionsan is normally a character that is awkward and lonely yet optimistic. I think that would translate to a lot of overt and clumsy attempts at solicitation: "I'm so lonely here. If only there was someone to help with that. The water is so cold, what could we do to warm up?" I think Onionsan would ramble wistfully about a whirlwind romance and mention how they long for a fairytale happy ending.

The "Bird That Carries You Over a Disproportionately Small Gap" probably does not exist (?): its iconography in canon suggests it is a young duck, and I think the difficulty having kids would mean this little guy doesn't get born. If we were to assume that the Little Bird does still exist (miraculously), there would likely be even more emphasis on how much they are cherished by the community (especially by Undyne).

There are 4 "Snails". Snail 4 (a seemingly regular eatable snail) would likely remain unchanged. Snail 1 (a long nosed snail that makes a lot of wordplay referencing the longness of his nose) might make some kind of big dick joke, maybe one about how size absolutely matters.

'Snail 2' is actually a green guy who bought the shell off Snail 3. I think in Underlust3r, instead of buying the shell to be a new home, he would have bought it as a new sex toy. Snail 3 would be counting its money either way.

I think (Tem Shop) Temmie is at least 21 in this AU, and works as a pole dancer/stripper for extra college money at least part time. They wear a yellow bikini with cyan hearts on it. I don't think this negates her role as a vendor in Temmie Village, though: I think if the player spends enough at her shop to put her through college, Temmie will get to quite stripping/dancing to pursue their business dreams with more success (and get away from all the big sweaty muscles of her usual clients -coughAaroncough-). I like to think she runs a successful clothing store. It is worth noting that, to remain true to the surviving canon, Shop Temmie's hair is brown. I think it would be cool if this was a botched bleaching job that she likes even better than the intended blond color.

The other Temmies are probably also strippers. I like to think they all specialize in some sort of kinky clothing fetish.

Hoi I'm Temmie! -- in a sexy dom leather outfit.

Hoi I'm Temmie! -- in a schoolgirl outfit.

Hoi I'm Temmie! -- in a sexy maid uniform.

Hi. I'm Bob. -- in a drag king three piece suit.

The mushroom dance guy, Ragel, does its little mushroom dance. Still, if the player has sex with anyone, it says the player sinned by having sex before marriage. (Why not have an allegory for religious conservatism regarding sex in the sex AU?) And if they DON'T, it wonders when the player is going to get married and start a family. He sheds a lot of spores but they never propagate.

The "Elder Puzzler" in Undertale canon resents that kids today don't appreciate puzzles. The "Elder Puzzler in Underlust3r resents that there are hardly any kids to show puzzles to, and that the adults only care for puzzles that let them wank in the end. Not that he minds a good kinky puzzle, but not all puzzles need wank!

Clam Girl is probably very happy to brag about how her neighbor in the city has a kid, given how rare and precious those are nowadays.

Canon Undertale's Snowdin is full of teenagers who play in the forest between town and the ruins -- thats the whole reason the Royal Guard patrols out there so frequently (to keep the kids safe). Without them, the patrols would be significantly fewer and the forest even more devastatingly empty.

There would likely be no Snowdrake, no Chilldrake, and no Ice Cap in Underlust3r.

I usually headcanon Jerry as being a bit older (20s), since many of his mannerisms remind me of the stereotypical freeloader-in-his-mother's-basement guy. But if I really look at his flavortext and how he engages with the characters around him, he's probably a teenager too. And as I cannot find any Underlust Canon of Jerry, I think he too wouldn't exist in Underlust3r.

(Although, if one were to say Jerry was one of the few miraculous kids still born safely, it could be really interesting: He would likely be a spoiled rotten brat used to getting everything he wants... A kid who doesnt understand that he's lonely, or who thinks being alone is a natural and unavoidable state of being. He would only really get to socialize online, so he would depend on undernet even more. what few other kids are in his community would be much younger than him and out of his peer group. there's nobody around to ditch him.)

Because there are so few kids, Gyftrot isn't going to originate Gyftmas quite the same way.

It could be there isnt a gyftmas tree at all.

It could be that the Gyftmas tree tradition is, perhaps, a convoluted result of some shibari play that gave folks ideas. Maybe the gift part started as aftercare. Maybe they realized it would be nice to have an excuse to give presents to the kids. Maybe there's this bittersweet melancholy because there are so, so few presents under that tree.

In other, lighter news: I like to think that someone vandalized the "Welcome to Snowdin" sign to say "Welcome to Snowdick".

In the Snowdin Woods, which we dont really see much of in canon, I like to think there is very little activity. With only Jerry and MK really playing out there, there isn't much need for all that much manpower to monitor it.

The sentry stations are all there, but they are very rarely occupied by anyone but Sans and Papyrus.

I think most of the traps are defanged and untended except when theyre being used for some kinkplay (which is only authorized at certain hours).

Now back to the play-by-play of characters:

Doggo is no-motion-blind, so I dont think he cares much for appearances. But I bet he loves when people wear tassels or dangly bits that flutter and sway with every little twitch. He probably asks for lap dances!

The Snowman is probably much the same as in canon, except his carrot nose is now his carrot cock. It wants to see the surface. It definitely has a voyeurism fetish. And maybe Snow-Tits.

Lesser Dog is the Royal Guard that grows its neck out longer and longer as it is pet. I like to think this is largely unchanged in Underlust3r, but the player would have the option to pet it or to 'heavy' pet it. (Which would affect the route -- pacifist vs genocide equivalents.) I also think that instead of building Snow Dogs, it builds Snow Dicks instead! (they are unnecessarily long.)

Greater Dog is a leg-humper. It has great penmanship just like in canon, but tends to decorate its calligraphy with hearts. Its armour is more sexualized in nature, giving it a hulking, yet busty amazonian silhouette. It is still a comparatively smaller dog inside the armor.

Gyftrot is tangled in gyftmas lights and silky red ribbons. It's got a bondage fetish that it's a little ashamed of, yet still wants to explore.

Dogamy and Dogaressa are so so so in love. Dogaressa is (usually) the top (and the dom) in their relationship, and Dogamy is so happy about it! (They switch it up sometimes so Dogaressa can feel taken care of too.) They already know dogs can pet dogs, and it's a big part of their relationship.

Glyde is an attention whore. It is also an exhibitionist. It enjoys both degradation and praise.

The Nicecream Guy is one of the few Snowdin residents with a little Canon Underlust material about him. He features in Papyton Comic Post #9, as well as a couple ask answers (like "does-nice-cream-guy-do-anything-special-on" and "so-if-bp-got-into-weird-ass-food-porn-and"). He canonically sells "Naughty Cream", and wears no shirt, with one red suspender strap. He's confident and flirty, and excited to be a part of any fun to be had.

Faun is a deer-like monster that you find near the Lesser Dog's station. In Underlust3r, he gets frustrated that he cannot actually have sex with LD's giant Snow-Dicks.

I like to think the Mice (which are the squeaking ones that you find near savepoints, which are referred to in relation to cheese) are one of the few creatures not doing too badly population-wise. They might be fewer in number, but they're still having smols.

In Snowdin Town:

The Snowdin Shopkeeper is a busty, pragmatic lady who sells homemade food and clothes. She mentions that she isn't licensed to sell anything else, but if you want a little something sweet for free she closes at 7.

The Inn Keeper that run The Snowed Inn is a rabbit that, in canon Undertale, has many children. In Underlust3r, that number would be significantly reduced. She only has one smol now, and she usually keeps it upstairs in a bedroom during work hours. The smol that would normally sit by her side at the front desk does not exist.

The NPC known as "Rabbit Kid" is "Rabbit Boyfriend" in Underlust3r. He is ~18-19yo and just starting to integrate into the kink scene. He thinks Rabbit Girl is hot, and gets shivers when she walks him on her leash.

In Undertale Canon, the NPC "Rabbit Girl" is usually paired with her little brother "Cinnamon", whom she walks on a kid harness. In Underlust3r, Cinnamon doesn't exist. Instead, she walks her boyfriend on a leash!

Gift Bear is shown putting a present under a tree in Snowdin. In Undertale canon, they explain that it is a tradition that started when teens started tormenting a monster by festively decorating it. Thus, the villagers would put presents under the tree as an apology. I think in Underlust3r, they would mention how there arent that many kids around anymore, but they started this tradition in hopes that there will be someday. They got the idea after some furniture-play with a Gyftrot, and it sort of stuck. Nowadays, though, Gyftmas is that time of year where everyone sets the kinkplay aside to celebrate the kids they do have, and hope to have later, and thank everyone around them for being a part of their family. (Family as in community.)

Politics Bear in Undertale canon wears an orange jacket. They mention that Snowdin has no mayor and that if there is ever an issue, "...a skeleton will tell a fish lady about it." In Underlust3r, I think their jacket would be purple or pink. They would talk about how Snowdin doesnt have much visit from the Royal Harem besides the residents that are enlisted, but if any trouble does come up, a skeleton will tell a fish lady about it. What does a Harem have to do with keeping the peace? That's politics!

Scarf Mouse is an NPC that is pessimistic about the Underground's optimism in Undertale Canon. Because they wear a scarf with stripes on it, one could interpret them as being a kid. In Underlust3r, I could see Scarf Mouse being reinterpreted a couple ways: Way (1) being aged-up, if still on the young adult side. Way (2) they're one of the few kids still around. Either way, they would express in dialogue that they love their community (either because of the freedom of expression or because of how supportive the adults in their life are), but that they are getting really tired of all the dick jokes. (They aren't good at making dick jokes.)

Red Demon is an NPC that, in Undertale Canon, is optimistic about the troubling situation of the Underground. In Underlust3r, they would complain about the LT epidemic and how in other territories monsters get too aggressive, but it is glad that Snowdin is so chill. If Scarf Mouse is a kid, Red Demon would be its babysitter; If Scarf Mouse is an adult, Red Demon would be its friend (and maybe fuckbuddy).

Slime Dad is a very lucky slime that has been fortunate enough to have TWO KIDS (just like in Undertale canon). And he is very protective of them! He makes sure to keep his kids inside after 6pm, even though the community kinkplay starts at 7pm: he knows his little scamps are always a bit late because they get so invested in their games, so he sets their curfew an hour early. Kids have a strict curfew in Snowdin! (For Safety!)

The Knock Lover NPC now has a Knock Fetish.

Ice Wolf would already go by Jimmy Hotpants (although I can't decide if I like that as his real name or as his Stage Name when he takes the stripper pole). His dayjob is the same as in Undertale canon: he throws ice into the river to cool the core. They might have an ice kink after spending so long being riled up around it.

The Library Lizard is the Librarby Librarian who is shaped like Alphys. Like in Undertale canon, they know about the sign typo. In Underlust3r, they have tits now. Yes, they are aware that lizards don't have mammary glands.

The Library Loox's dialogue in Undertale canon is affected by the player's choice between Junior Jumble or Crossword being more difficult. In Underlust3r, I think it would be fun if the question was whether being the Dom or the Sub in a scene was more tiring. (And after the Undyne exchange, he would mention how they both need aftercare either way). I also think he would be more pink in color.

There are two Newspaper Editors:

Newspaper Editor 1 is "Scarf Rhino". She talks about how there's no news, so the Newspaper generally prints "comics and stories" (hentai and erotica). She likes including word searches and little games on the last page, even though they arent as popular. She is trying to write a romance novel.

Newspaper Editor 2 is "Lady Garf", or Game Cat Garf. She's the "number-one word-search creator in the entire underground!" She loves that her friend keeps supporting her passion, even though the word searches aren't as popular. She mentions she has two diehard fans and getting their feedback keeps her going.

Then there are the NPCs in GRILLBY's bar.

In Underlust canon, Grillby's Bar and Grill is instead Grillby's Strip Pub. It is depicted in Papyton Comic Post #6, as well as a reblog art RP with someone's OC. It has been shown with multicolored lights and stripper poles in view of the bar. It has shown faceless silhouettes, some of which are clearly shaped like rabbit monsters, and others with Devil horns. Most Undertale canon bar-goers haven't been actively depicted in Underlust canon.

"Big Mouth" is the toothy monster in Undertale canon that tells us how monster food works, and the difference between it and human food. In Underlust3r, this guy definitely has a food fetish (and maybe an omorashi one too).

"Drunk Bun" in Undertale canon is bored, wants new drinks and hot guys, and flirts with Sans on screen in a brief exchange. I think that all would apply to Underlust3r too! I think she has huge tits, likes pole dancing even when she's too drunk to keep her footing, and loves to order food that Grillby heats up with his mouth (even though that service costs extra).

"Ugly Fish" in Underlust3r is very different (because I had fun thinking of how the geopolitical landscape would affect him). In Undertale canon, he's looking for a girlfriend and having trouble, both because he is socially awkward and also because his looks are less than conventionally attractive. In Underlust3r, I think the LT would affect his appearance in a way that would make him very appealing (bright reddish fish coloration like some breeds of fish take on during mating season). As such, with the increased libido and many many desperately horny monsters now at large, I think Ugly Fish would be so inundated with suitors that he would be overwhelmed to the point of distress. He wears a bag over his head to hide from his many stalker "girlfriends". His dialogue would tell us that he doesn't know who spread his phone number around, but now he needs to change it. He's grateful for the Pub (cuz Grillby doesn't tolerate any nonsense) and also is grateful that Sans offered to teach him self defense.

Red Bird has a voice and accent fetish. They tease Grillby about his all the time, and gang up on Grillby with Sans to fluster him about it.

Punk Hamster in Undertale Canon is already against the Urbanites from the Capital and New Home coming in to Snowdin, saying it will erase the local culture. He also says he would like to see "some city slickers slip onto their butts!" I think these sentiments would be even more true in Underlust3r, where it is well known Urbanite monsters have a statistically significant increase in sexual aggression compared to rural Snowdin monsters. (And the Snowdin folks dont take kindly to that no sir). Punk Hamster looks very young for his age, and he plays that up on the kink scene. He drinks virgin mixes to keep up his jailbait persona (even though he's been a regular at the Pub for years and everyone knows it).

I think Punk Hamster is a very good segway into another thought I had regarding LUST: I think the type of monster they are can vastly change how LUST affects them.

Most of the monsters in Snowdin are Mammal-mimics (they aren't actually mammals at all, but their bodies mimic the shape and function of mammals in many aspects)! Since the strain of LUST is also from a mammal (humans are mammals), I think it is easier to digest, process, and control the effects of LUST for mammal-mimics.

Many of the monsters in Waterfall are also biological animal mimics, so while their compatibility is a little lower, they too have an advantage over, say, the completely non-biological and inanimate-object base of many of the monsters in Hotland.

Not that Compatibility is the only factor in how LUST affects a monster (Grillby is a non-biological monster and he processes it splendidly), but I think it's one of those major factors!

And finally, I'm also going to mention Monster Kid here! And this is going to brush close to some sensitive themes, so brace yourself.

Monster Kid exists in Underlust3r, because I think he is a very fine character to have for the area to tell its story.

Instead of following the human around in Waterfall, I think he would follow the human around in Snowdin Woods (under Sans supervision). He would drop the loredumps about there being so few kids his age to play with, how excited he is to meet someone new!

I want to quote an ask answer Niel gave us: "Of course, only monsters that are of age get injected. Kids are just kinda used to the way things are because it’s all they know."

Monster Kid is probably in his teens. He knows he has a curfew because adults play at night. He knows there aren't as many other kids to play with because that is just the way it is. He knows that his parents are getting more and more anxious about something every time he has a birthday, every time he gets older, and gets closer to the age of majority.

He's excited to grow up! He's excited to get to play adult games and learn what happens in the Pub at night when the music gets loud! But he isn't an adult yet: he's a kid, and he doesn't really understand why his parents moved all the way to Snowdin, why there needs to be a curfew, and why they get so anxious about him growing up. He doesn't understand why he can't go to Waterfall without a babysitter, or why he isn't allowed to go to Hotland at all.

He knows LUST is a thing adults get, but he doesn't understand what it is or what it does or why they get it.

He doesn't understand why the adults in his life make those upset faces when he says he wants to be in the Royal Harem just like his hero, Undyne.

I think a lot of very delicate, but important social commentary could be tackled (by someone more adept than me, maybe) with the use of Monster Kid in Snowdin. Something something age-appropriate conversations something something personal responsibility something something kids aren't stupid but they do need to learn to respect adult boundaries because boundaries inherently deserve to be respected something something i dunno.

(That was over 3k words holy shit should i be archiving this stuff to AO3???)

Battle NPCs

Vulkin mistakenly believes its lava can heal people. In Underlust3r, it mistakenly believes everyone is into temperature play and watersports. It also thinks its lava counts as watersports.

Tsunderplane in Underlust3r is largely the same, except with the added flavor of being a domme that likes to run over its subs (although it is careful not to entirely crush them... unless they're into that).

Pyrope in Underlust3r is definitely the master of shibari. It wants to tie you up so badly. It also has a sweat fetish, and loves temperature play too (the hotter the better).

So Sorry was added as an enemy in 2018, around or after Underlust's original canon was discontinued. One interpretation you could make from this is that So Sorry does not exist in Underlust3r. That being said, I like to think So Sorry is in Underlust3r, and that they are an artist that draws fetish art. He's very excited to take commissions , but is not very confident in himself since he is self conscious about all the hardcore BDSM and noncon fetish art he draws (although a lot of it is by commission). If it thinks it missed a tag or warning it apologizes endlessly for the inconvenience.

Royal Guard 1 (RG01) is a rabbit monster in full plate armor. I think the armor stays on during and he is still incredibly gay for RG02.

Royal Guard 2 (RG02) is a dragon monster in full plate armor. I think the helmet and boots stay on during, but the chestplate comes off for his boyfriend (RG01).

I think these two specialize in poly and orgy services, alway doing their duty in the Royal Harem together.

Muffet in Underlust3r is freshly turned 18 and has just been given LUST. She's still a little bit wild, riding the high of her new condition and sexuality. She is still flat in the chest compared to most monsters that develop tits, but she has developed curves in the hips and butt. When she isn't stripped down to her thigh highs and skimpy black outfit, she wears lolita clothes to signify she wants her space and isn't in the mood. She sells not only baked goods but also pinup photos of herself. Her OnlyFans equivalent has photos and videos of her doing sexy silk/ribbon dances (although she can also pole-dance when that's more convenient)

Overworld NPCs

Clam Guy :: This is the clam-headed monster that hangs out by the first Hotland water cooler. He talks about how he came to Hotland from Waterfall specifically to get a drink. In Underlust3r, he comes to Hotland for the same reason (just sluttily).

Business Dude is canonically a Dragon in a blue 3-piece suit. In Underlust3r, i like to think he would still wear a suit (for kink reasons). Although his pants may be assless chaps. He watches Mettaton for the news, and appreciates how he can rely on him to know when he has to go to work or not. He thinks it would be more popular with some additional CGI, maybe of sexy dancers.

Fire Coffee is a black wisp or black fire monster holding a drink with a straw. In Undertale, he talks about how Mettaton has 2-3 dozen fans (in a positive light). In Underlust3r, I think he would talk about how Mettaton has only 2-3 real fans, which is a shame since his show is actually really good. (despite the lack of bouncy tits)

Fox Head :: This monster speaks in dialogue ending with a question or a question mark. They are Business Dude and Fire Coffee's co-worker. In Underlust3r, they are still frustrated because neither of their coworkers wants to go to work -- after all, it's glory hole day?

Fuku Fire :: The green fire monster who usually wears a japanese schoolgirl outfit. She normally talks about loitering. In Underlust3r, she probably doesn't exist. If she does exist, she wears a schoolboy uniform instead (to deter anyone looking for jailbait). She talks about how she can't wait to grow up so she can loiter wherever she wants.

Skateboard Girl :: The purple monster in a schoolgirl uniform. In Underlust3r, she probably doesn't exist. If she does exist, she wears a boy's school uniform (with the long pants). She complains that there aren't enough kids her age to become friends with, and how it feels like there is no point going to such an empty school.

Heats Flamesman :: A small, flame monster. He largely doesn't change in Underlust3r, being an NPC that wants to be remembered by name. (Hearing his name is a kink to him.) He wears a black thong.

Hot Dog Harpy :: This monster is seen near Sans's illegal Hot Dog stand. In Undertale, she comments on the fact that he has not cleaned the snow off of the roof of his Hot Dog stand, and deems it a result of his laziness. In Underlust3r, I think she would joke about how his stall is the only place in Hotland to enjoy cold temperature play (although she still thinks it's a lazy way to go about it).

Hot Dog Vulkin :: This Vulkin can be seen near Sans's illegal Hot Dog stand. It expresses joy over having obtained a Hot Dog. In Underlust3r, I think it would be a little freak (affectionate) who enjoys putting hotdogs in its top way too much.

Scared Donut Guy :: In Undertale, this monster was scammed by Muffet into spending all of his money on her pastries. In Underlust3r, I think he would still get scammed by Muffet: he wishes he had bought more of her pastries than he did, because he really only needed one of her pinup photos and now he is out of donuts.

Diamond Boys 1&2 :: In Undertale, these two monsters show up after solving the 3rd Floor's north puzzle. They're fans of Mettaton. In Underlust3r, I think they probably don't exist.