monkye :)

Both the broom closet "ending" and the genocide route of undertale are commentary on how players in a videogame based around choice will almost always stop interacting with the story emotionally, and begin treating the game as explicitly a video game, just so they can exhaust every possible choice and route it has to offer.

The Broom Closet "Ending"

I say "ending" in quotes because it's not even an ending. The game never restarts, and you are always free to leave the closet at any time and get any actual ending that comes after the employee meeting room. It only "ends" because the narrator eventually stops talking (which, granted, is nearly the same thing, see: the Zending and Apartment Ending; also Whiteboard Ending for commentary on what counts as an ending).

In usual Stanley Parable fashion, most of the analysis is done by the Narrator himself, very explicitly, out loud, but easy to miss if you're not engaging with it as analysis. What frustrates him the most about the situation is that there's nothing to do in the closet, assuming you're still engaging with the game's story. There no new choice to be made, no indication that there would be one, not even a prompt to make another choice as it tradition in the game ("He entered the door on his left" and similar cues).

Then the Narrator prattles on about how there's literally nothing to do in the broom closet, etc, etc. What he comes close to realizing but never quite does, is that him ranting about the broom closet is precisely the point of the Broom Closet "Ending". There's nothing relevant to the story or universe or the game here. The only reason people stay in the broom closet for more than 10 seconds is that they've completely abandoned caring about the actual story, and their suspension of disbelief.

Not that the game actually judges/moralizes you for that. The story is paper-thin. Stanley is a non-character, maybe even the quintessential non-character. It's a parable, it's not meant to have worldbuilding or lore beyond what's needed to expose its points. The Narrator and the logic of the world change radically and inconsistently with each ending to better serve its purpose. Interpreting this ending as the devs whining that people would follow a choice they coded in is, I think, doing a major disservice to the cleverness of the writing in this game.

You stay in the broom closet because, on some level, you are keenly aware that games are made by people, with only finitely many paths coded in (sorry, Raphael), and that the Narrator acknowledging you is the ultimate proof of there being something to do. In continuing down this path, you have to completely stop caring about the game on a story level. The devs ensured this by making the broom closet utterly boring: there's literally nothing else to do in that thing (it's a broom closet!).

Interestingly, the Narrator very quickly matches the player's detachment, beginning to addressing them as "you" and implicitly being aware of there being a real person behind Stanley. He then starts going on about how you'll mention this event as "OH, DID U GET THE BROOM CLOSET ENDING? THEB ROOM CLOSET ENDING WAS MY FAVRITE!1 XD" to your friends.

This happens completely without fanfare too, the pronoun switch is done within one sentence and the narrator never goes "oh you're a real person"; there's a whole other ending where the main point is the Narrator reaching that conclusion. But here there's no point, because to reach this dialogue in the first place, the writers know you must have already revealed yourself as a real person playing a video game, so he doesn't need to play coy.

Interestingly, the Broom Closet "Ending" is also one of the very few endings that "reward" you with a lasting effect beyond a restart: if you go back in the closet on the next restart, the Narrator flips out and leaves you without further dialogue. If you restart once more after that, you find the closet very amusingly boarded up. In the Ultra Deluxe bucket version, you get stickers that stay on the bucket for the rest of your save file.

Undertale's "Genocide" Route

I hope the parallels became clearer with my above explanation. The main commentary made about this route is that carrying it out requires the player to, again, detach themselves from emotional involvement in the story and characters (which is a lot more significant here than in TSP), and begin treating it as a mere video game, with XP to get, LV to gain, bosses to beat, and crucially, routes and events to exhaust.

The route is filled with comments that point toward this, and I don't know if it's really pertinent to list them all, so I'll just give a few illustrations.

Flowey puts this almost as explicitly as the Narrator. He recounts how once he got the power to SAVE, he initially still cared about the people of the underground, until that bored him and he started treating the Underground as a giant dialogue/story tree just to see what would happen.

Many characters comment on how the player is not really a human through the route. It's both a way of highlighting their in-universe cruelty and also a correct assessment that if you are motivated to see the route to its end, you've already given up on embodying an actual human within the story of the game, and that you're here to see what happens, to exhaust every path that had to be manually coded in by Toby Fox.

This is also the ending where the SAVE mechanic is the most explicitly discussed. It's still a thing in other routes, and still part of the story there, but it's no coincidence that Genocide draws attention to the video game mechanics you're using to treat Undertale as just a video game.

It is also, very famously, the ending of Undertale that permanently (short of messing with game files) affects your save files and "taints" any subsequent Pacifist endings. Just like TSP, it acknowledges you engaging with it as a video game, by giving you a ""reward"" that crosses over resets and restarts.

Similarly, I've seen people online frustrated with Genocide, interpreting it as Toby Fox putting himself on a moral high ground, admonishing the player's morality for being evil while playing the route. Just like in TSP, I think that's missing the point, and a disservice to the game's writing. I think the route is meant to make you feel bad, insofar as it tries to draw attention to how you remove yourself from caring emotionally about very endearing characters. But I don't think Toby Fox is over there moralizing players for playing a huge route he explicitly and painstakingly coded into his game.

The route makes you feel bad because these are characters you're supposed to care about, and because the grinding gameplay is boring as fuck (just like the broom closet). This is so you realize that your motivation for pursuing it lies outside of the story of the game, and within the fact that you are a real person playing an actual video game made by another person, as opposed to an interactive documentary of the Underground.