Undertale, but all the AU's are actually different games made off like Undertale, like uh... Sonic games!
Games in chronological order (what came first)
๐จ๐ป๐ฑ๐ฒ๐ฟ๐๐ฎ๐น๐ฒ is the Classic.
๐จ๐ป๐ฑ๐ฒ๐ฟ๐๐๐ฎ๐ฝ was released on opposite day.
๐จ๐ป๐ฑ๐ฒ๐ฟ๐ณ๐ฒ๐น๐น was made with edge in mind. (like shadow games, the dark horse)
Haventale (multiplayer where no human souls are taken, but you cant ever leave the underground. Hide and seek with NPCs and other players are available.)
๐๐ฎ๐๐๐ฎ๐น๐ฒ (for the cat lovers of course! They were planning a dog game but decided against it...)
๐๐๐๐๐๐ฎ๐น๐ฒ (were SOMEONE goes crazy from all the genocide resets and thinks they can only win one way)
๐๐ฎ๐ป๐ฐ๐ฒ๐๐ฎ๐น๐ฒ (for all those dance dance revolution fans! You have to have the full body thing for VR though... This game can teach you to dance whatever style you want as long as you try hard enough!)
๐๐ผ๐ฟ๐ฟ๐ผ๐ฟ๐๐ฎ๐น๐ฒ (was made to be a literal horror game for... Yeah, I see you. Freaks.)
๐๐ถ๐๐๐๐๐ฎ๐น๐ฒ ๐๐ถ๐๐๐๐ฏ๐ผ๐ป๐ฒ๐ (a multiplayer platform where you can live a day to day life with a bitty of your own! A person can only have up to 4 bitties so choose wisely! Originally named bittytale but the players demanded it to be changed to bittybones.)
๐๐ถ๐น๐น๐ฒ๐ฟ๐๐ฎ๐น๐ฒ (were our ghost companion is actually a demon, gets bored, and convinced someone to kill everyone, it's like a murder mystery. Also, released on Easter)
๐ ๐ฎ๐ณ๐ถ๐ฎ๐๐ฎ๐น๐ฒ (for the ones who want angst and family as they got mommy or daddy issues, with a side of murder mystery)
๐๐น๐ผ๐๐ฒ๐ฟ๐ณ๐ฒ๐น๐น (unlike most of the games, this one you get a limit of tries you can take! Oh, and you get a romance with the sans of this one if you try hard enough to interact with him! The franchise hated this one and wanted to delete it though...)
๐๐ฐ๐ต๐ผ๐๐ฎ๐น๐ฒ (a thirst trap with lore hidden all around, explaining the Multiverse theory and having a bunch of Easter eggs, and released on Easter just to tease people even more.)
๐๐๐๐น๐๐บ๐๐ฎ๐น๐ฒ (You can choose to be a nurse or a patient! Slightly horror themes though...)
๐ ๐ฎ๐ณ๐ถ๐ฎ๐ณ๐ฒ๐น๐น (basically a shooting game with how much those fighting cutscenes happen)
๐ฆ๐๐ฎ๐ฝ๐ณ๐ฒ๐น๐น (purple version, like pokemon)
๐๐ฒ๐น๐น๐๐๐ฎ๐ฝ (red version, like pokemon)
๐๐ฟ๐ฒ๐ฎ๐บ๐๐ฎ๐น๐ฒ was slightly strange game (it was made for self awareness and to show people shouldn't bully others because they are different.)
๐ฃ๐ผ๐ธ๐ฒ๐๐ฎ๐น๐ฒ (with the permission of the creators of Pokemon, the Undertale franchise made a game for the pokemon lovers in the franchise, where monsters and humans are in peace and catching pokemon together!)
๐จ๐ป๐ฑ๐ฒ๐ฟ๐น๐๐๐ (not for those under the age of 18, MDNI. Released on the day before Valentine's, so some people wouldn't be lonely)
๐จ๐ป๐ฑ๐ฒ๐ฟ๐ณ๐ฟ๐ฒ๐๐ต (this game is unstable, and may seem happy but be warned, you shouldn't be near the sans for too long... Actually, try to avoid all the residents infected with neon colors.)
๐๐ณ๐๐ฒ๐ฟ๐๐ฎ๐น๐ฒ (just a chat game where you talk to an AI named Geno, that, when used to you, slowly gives out hints of lore about why they are in this void, where their game used to be)
๐จ๐ป๐ฑ๐ฒ๐ฟ๐บ๐ผ๐ป (monsters are pokemon!)
๐๐ฝ๐ถ๐ฐ๐๐ฎ๐น๐ฒ (with EPIC fighting scenes for the anime lovers)
๐๐ฒ๐บ๐ผ๐ป๐๐ฎ๐น๐ฒ (the underground is actually hell, and monsters are demons)
๐น๐ถ๐๐๐น๐ฒ๐๐ฎ๐น๐ฒ (more of an kids educational game, and you can choose your grade level before hand and you learn with the monsters of the underground! 1st grade to 4th grade only tho [education mode optional])
๐ข๐๐๐ฒ๐ฟ๐๐ฎ๐น๐ฒ (mostly known for it's wonderful artwork, but is an educational game as well! 5th to 8th grade! [education mode optional])
๐ซ-๐๐๐ฒ๐ป๐ (it's like a CROSSover of some of the popular games in the franchise)
๐ฆ๐ฐ๐ถ๐ฒ๐ป๐ฐ๐ฒ๐๐ฎ๐น๐ฒ (another educational game, but for 9th grade to college [education mode optional])
๐ก๐ฎ๐ด๐ฎ๐๐ฎ๐น๐ฒ (Snake Bois ๐)
๐ฆ๐ถ๐
๐ฏ๐ผ๐ป๐ฒ๐ (a sade tale and an angsty game, like horrortale! Perfect for the freaks of the franchise-)
๐๐ฒ๐น๐น๐ณ๐ฟ๐ฒ๐๐ต (where the UNFRESH people resides! PUNKS!!)
๐ฅ๐ฒ๐ฎ๐ฝ๐ฒ๐ฟ๐๐ฎ๐น๐ฒ (kinda like God of War games?)
๐๐ฟ๐ผ๐๐๐๐ฎ๐น๐ฒ (a prequel to X-Event, released after X-Event to tease the People who wanted to see more lore)
๐๐ฟ๐ฒ๐ฎ๐บ๐๐๐ฎ๐ฝ (was released a year after Underswap, on opposite day to celebrate the franchise's success)
๐ก๐ถ๐ด๐ต๐๐บ๐ฎ๐ฟ๐ฒ'๐ ๐ฅ๐ฒ๐ฎ๐น๐บ (another Rare replay inspired one, and only hold the "violent games" that the gang are from. Has some cutscenes of the Nightmare gang just vibing, being friends, and hanging out if you wait long enough, like their waiting for you to start up their game so they decided to do something more fun for a moment)
๐ข๐บ๐ฒ๐ด๐ฎ ๐ง๐ถ๐บ๐ฒ๐น๐ถ๐ป๐ฒ (a game that actually have most of the timeline games available on it, like Rare Replay, with Core Frisk as a guide!)
๐๐ผ๐ผ๐ฑ๐น๐ฒ๐๐ฝ๐ต๐ฒ๐ฟ๐ฒ (a game that actually has most of the AU games available on it, kinda like the Omega Timeline but with -๊๊๊- as the guide!)
๐๐ป๐๐ถ-๐ฉ๐ผ๐ถ๐ฑ (the last game of the franchise. A void with an AI that is kinda like Geno, but not as much lore and is more focused on explaining the AU's, the AI is called ฦๅฐบๅฐบรๅฐบ and they could show you ๐๐ฏ๐ฏึ
๐ฏ from all of the games in the franchise... But if you want the cutscenes you got to pay for the cutscenes... Or sell your soul to the franchise)
๐๐ฎ๐๐ฎ๐น_๐๐ฟ๐ฟ๐ผ๐ฟ (were the AI in Aftertale gets corrupted after having a run in with Error, A timeline game)
Now after this it gets a bit weird, as some AU's are if the NPC acts different, showing different routes, like how Dusttale was an alternate timeline of Undertale.
Timeline games are made with the AU game it's based off in mind, and it has some of the same lore as the AU game it's based off. And Mixed AU's like Swapfell would be... An AU game that takes traits from both AU's. (like the AU's would be parent AU games to that game.) Also, timeline games are side games that are just for fun.
Killertale and Dusttale are like cousins, with the same uncle.
I think in this idea the Franchise would have a saying like,
" We aim to please all of our audience! So do enjoy the games!"
And the franchise would hide something like the FNAF franchise did in game, like how they needed 7 human souls to make the original game. They need 7 for each game...
Yeah the franchise is slightly evil...
(don't get on my ass I know this isn't the actual release order of the aus, I just wanted it to make more sense-)