Skip To Content

    10 Undertale AUs That Have Taken Over The Fandom

    Undertale is a great game, with a fandom that as gone completely AU Crazy! Here is a list of some of the most prominent AUs

    1. UnderFell

    underfell.tumblr.com / Via undertaleau.tumblr.com

    Probably the most popular, this AU takes the "Kill or be Killed" motto to a whole new level. Starting as a design aesthetic, the fandom has created some ground rules- with monster SOULS not made of love, but of LOVE, and a more red oriented color scheme. Interpretations of this range from serious to comedic, and it seems to have endless variations, comics, fanfics, and ask and RP blogs.

    2. UnderSwap

    popcornpr1nce.tumblr.com / Via undertaleau.tumblr.com

    Personalities swapped all over the place! This is pretty much Undertale, but everyone has flip flopped personalities (and clothing styles, apparently). Its mostly cute and comedic whenever drawn or written about, but some people have been able to do some really fascinating twists on it. Underswap Papyrus seems to be a favorite in the fanfic community (I can't imagine why... oh wait yes i can).

    3. Gaster Blaster!Sans (And Occasionally, Papyrus)

    magolorssoul.tumblr.com / Via undertaleau.tumblr.com

    You know those beastly skulls that Sans kills you with repeatedly in the Genocide run? Well, in this AU He (and sometimes Papyrus) can turn into those, with full bodies and dramatic transformations! This AU is mostly known by its voicework (by Sushiinfood on Tumblr) and the small but very talented Fanfic community, though there is some very impressive art. Theres even a subsection of this AU known as Baby Blaster (Popularized by Keetah (SpaceCat) and their fanfiction- Trust) where they are created/born that way. Theres a surprising amount of variety

    4. Gaster!Sans

    borurou.tumblr.com

    The fan favorite mystery character WD Gaster and Sans fuse to create the mysterious Gaster!Sans. Originally created by Tumblr User Borurou, there are many popular interpretations of this character from "Stone Faced Asshole" to "Mob G and Kitty Cat" to "Comic Jens". Seems to be a favorite with the ladies... for some reason. But other than that people have made a lot of fun, funny, and fascinating interpretations of this character, even going so far as to cross him into other AUs

    5. YandereTale

    ammazolie.tumblr.com / Via tumblr.com

    A very *very* NSFW AU that has taken on a life of its own in the hands of its talented creator, Ammazolie. A completely traditional artist, her art is what you see first and foremost when it comes to this AU. The story behind it is complicated and depends mostly on character interaction, but boils down to Yanderetale Papyrus cursing his timeline to soullessness. Its a deep dive, but worth it. Just make sure you're not squeamish, and that you're 18 +. Theres gore, sex, and other disturbing themes.

    6. MobTale (UTMob)

    nyublackneko.tumblr.com / Via tumblr.com

    Called by a variety of names including "Mafiatale" and "Undermob", the most famous version of this is the rendition called "UTMob" by the artist "NyuBlackNeko". There is also a popular Mobtale Fanfiction called "Never A Lovely So Real" that is popular in this portion of the fandom. Its basically the monsters as an underground mob - Godfather style. With Asgore as the don, Undyne as his Consglire and so on. Theres many variations and lots of great fanfiction.

    7. ErrorTale

    loverofpiggies.tumblr.com / Via tumblr.com

    One of two AUs by the same creator on this list, this is perhaps the more prominent one? Depending on where you are in the fandom, at least. The premise is that this particular Sans' timeline has gone batshit glitchy, and he's gone cuckoo for cocoa puffs and goes around destroying AUs to "cleanse the mutliverse". The canonical stories are cataloged on AskErrorSans on Tumblr (which is currently on haitus). Its a fascinating AU with not a lot of variation, but many stories to tell

    8. Inktale

    comyet.tumblr.com / Via comyet.tumblr.com

    Created as the polar opposite to Error!Sans and Errortale, Inktale is an AU where the Undertale Cast (though its about 90 percent Sans if we're being honest) creates, maintains, and encourages the creation of new Undertale AUs to counteract Error!Sans' destruction. Theres a lot of love/hate art between the two, and some genuinely good fanfiction about their fighting. The AU itself has an interesting backstory, and the creator, Comyet, loves encouraging creativity with it- practice what you preach and all that!

    9. UnderFresh

    loverofpiggies.tumblr.com / Via tumblr.com

    This ones a bit of a doozy! So, follow with me here: in this AU, there is a Parasite that infects its host, apparently taking over (eating????) its soul and seeking others to destroy. But the backstory is secondary to the character of "Fresh"- who the creator, loverofpiggies, has turned into their own character for creative purposes. People love this interpretation of Sans, who walks and talks that "sups cool yo" 90s lingo, secretly hiding an emotionless demon right beneath the volatile surface. Theres not much in terms of fanart but the RP community for him and his kiln is surprisingly robust. Also fanfiction. Lots of fanfiction

    10. Basically anything having to do with the origins and story of WD Gaster

    Anything, from fan comics like "Dogs of Future Past" and "UnderRift", Fanfics like "A Year Every Minute", and even every single mention of this Character that claims to know his origin, WD Gaster is character with no dialog, that only appears once in every 500 or so playthroughs of this game. He's a mysterious character with 101 different interpretations, which let to the absolutely fabulous and fantastic EchoGaster Project, which you should totally watch right Here . But regardless, Gaster might be one of the biggest characters in the fandom.... despite being a complete mystery. Fascinating, Huh?

    What are your favorite Undertale AUs? Any popular ones I missed? Comment on it!