this is what the characters do, or how they operate in the story, along with personalities. some of these are subject to change, along with designs! this is an ongoing au after all. 

sans: papyrus swap. his goal is to join the royal guard, but not really for himself. it’s more to prove himself to his little brother, who has been in the royal guard for years. instead of puzzles, sans sets up traps around snowdin for chara to trigger. also, he is not innocent, nor does he pretend to be. he’s a dumbass bastard and he fully knows it. he is nice, but if you make him angry, he will spit in your food when you’re not looking and then serve it to you. he is also a terrible cook. if he offers a friendship meal, run. your stomach will not survive it.

papyrus: sans swap. he’s been in the royal guard for so long that it no longer phases him, so he’s grown lazy about it. he loves his job, but it doesn’t have all the glamour that it used to have. he also likes to eat healthy, balanced meals, and is an amazing cook. however, his job keeps him so busy that he doesn’t have the time to cook. 

alphys: undyne swap. big and scary, but only really when she’s in the mecha. however, while chasing chara into hotland, she trips, and instead of dehydrating, she falls into a panic attack, which chara nervously helps her through, confusing alphys. she definitely fits into the jock archetype. she isn’t in the royal guard, but she is a hometown hero for waterfall. think vigilante for alphys. despite everyone clamoring for her, she excludes herself from any social interactions as she’s made mistakes in the past that cause her to believe she doesn’t deserve any of the attention. nervous out of mecha, confident in mecha. 

undyne: alphys swap. undyne is the royal scientist, though she generally enjoys thinking up things to destroy humanity or at the very least cause harm to them. once chara falls into the underground and undyne has sights on them, she begins to make passive aggressive comments on her account on the undernet about them. she’s very stuck up at first, but as chara progresses and undyne sees that they aren’t that bad, she slowly softens and starts to help, especially after chara meets and begins to deal with the eccentric nature of napstabot. she enjoys mech anime and kaiju movies, and helped alphys make her armor. 

temmie: flowey swap. temmie does go by she/her, though asriel goes by he/him and maybe even they/them. originally, before being taxidermied, temmie was the original royal pet. she was there around the time that frisk fell and when asriel died, his dust falling on top of her. a few days later, she died as well. undyne, instead of using buttercups, decided to use the taxidermied temmie in her dt experiments, causing temmie to ‘come to life’ and become a vessel for asriel. asriel/temmie is angry because frisk was an angel, and didn’t desrve what happened to them. there are also multiple other temmies, all in queen toriels throne room. 

flowey: temmie swap. generally kept as common pets. they bounce up and down and speak basic english. you’ll see one in almost every shop and home. however, some versions, like echo, aster or golden are not generally kept as pets for a very simple reason: they have a tendency to, on some occasions, predict the future. 

toriel: asgore swap. instead of demanding the death of humans, she demands that the humans be brought to her for her to raise. however, monsters have a tendency to over estimate their magic in battle or over estimate how much humans can take, or they’re just plain terrified of humans and kill them in a moment of terror. toriel weeps over the fallen souls that are brought to her, and instead of keeping them in capsules near the barrier, she keeps them in capsules close to her so that she can watch over them and make sure that they’re safe and secure at all times. when chara gets to toris fight, shes fighting chara because she’s admittedly terrified of going up to the surface, and she doesn’t want chara to leave just yet. what would the humans think of them coming up with a teenager? probably horrible things. 

asgore: toriel swap. he lives in the ruins. gardening every inch and making rounds to make sure every flower has been watered. that’s how he finds chara and temmie. generally, he rushes humans out of the ruins, trying to convince himself that they’re evil and bad. however, every time he grows attached, and cries when the human leaves. he grew especially attached to chara.

chara: frisk swap. chara falls into the underground because they’re angry at the human world and all of the hate inside of it. they’re a severely misguided kid with a tendency to lash out at those around them and to think the worst of everyone they meet, always assuming they have an ulterior motive or that they’re evil in some way, like they think they are. their journey is about coming to peace with themselves and the world around them, and learning that not everyone is bad or out to get them and that people can and do care about them. they learn that they can be soft and trust others and that freeing the monsters would be a good thing, because even if their is evil on the surface, there’s good, too, and freeing the monsters would add to the good of the world.

frisk: chara swap. frisk is the first human to fall and befriends asriel. they become best friends, but somehow, frisk manages to actually confuse buttercups with edible food, eating them and accidentally poisoning themself. frisk is a pacifist at heart, and believes that everyone is good.

mettablook: napstablook swap. he maintains the small snail farm while also being a struggling fashion designer. his wish is to create fashion for everyone of all shapes and sizes, though it’s hard with  low amount of money, so he works many jobs around the underground, even helping asgore with his plants. the different areas of the underground also serve as inspiration for him. 

napstabot: mettaton swap. the body made by undyne was perfect in many aspects except one, its low energy combined with his own low energy. to combat this, undyne made a special charger for him, giving his body and his soul an extra pep. he makes sick beats and seems super happy and charged up, but it’s all thanks to the charger. he can also only be out for short periods of time before his charger starts running out of juice and he has to leave or else he’ll ruin his star reputation. in battle, you would win by knocking his charger off. 

grillby: muffet swap. he still doesn’t talk very much, instead preferring to play an exciting game of charades to communicate. around the underground, he owns many food carts, all ran by his fellow flames. they sell the same foods as in the game.