It is a crossover AU combining Undertale with the Super Mario universe. It uses the sprite-comic format, and follows a fallen Toad's journey through the Underground, meeting some familiar faces along the way.
About the AU
As stated above, Undertoad is a crossover AU with the Super Mario series of games. The player character is a Toad, who just fell underground through a mysterious hole.
- The RUINS are now blue, to match the popular color scheme of the Underground levels from Mario games.
- Jumping is a new mechanic added, for solving puzzles by breaking blocks, or, shown in Part 12, for secret platforming segments.
- Badges are a new mechanic added, similar to how they work in the Paper Mario games.
- Flowey is replaced with "Fiery the Flower", a fire flower who isn't as friendly as they seem.
- Toriel is replaced with Kammy Koopa, Bowser's right-hand assistant from Paper Mario and Paper Mario: The Thousand Year Door.
- Napstablook is replaced with a Boo of similar nature, named Napstaboo.
- Sans is replaced with Mario, everyone's favorite plumber. He's more laid back than usual and doesn't care much about capturing Toads. He helps you out throughout Snowdin, such as scaring off Jr. Troopa and giving you the Happy Heart badge.
- Papyrus is replaced with Luigi, Mario's younger brother, who dons his Mr. L outfit from Super Paper Mario. He wants to capture a Toad to get into the Royal Guard so he can finally be paid attention to. He is the main obstacle throughout Snowdin, setting up puzzles and schemes to capture the Toad. They always backfire.
- Undyne is replaced with Daisy, the hot headed now ex-princess of Sarasaland. She is captain of the Royal Guard.
- Alphys is replaced with Peach, ex-princess of the Mushroom Kingdom. She is the Royal Scientist for reasons not yet known.
- Asgore is replaced with Bowser, king of the Koopa Kingdom, and now king of the Underground.
- Asriel is replaced with Bowser Jr, Bowser's son. He is stuck as Fiery the Flower for reasons yet not known.
- Muffet is replaced with Donkey Kong, who sells bananas to make a fortune in the RUINS.
- Jr. Troopa, the mischievous Koopa kid from Paper Mario, is a boss fight in Snowdin. Don't step on his playground.
- Parakarry, the mailkoopa partner from Paper Mario, is also a boss fight in Snowdin.
- The true name of Chara has been replaced with "Shruby". Everyone thinks that Shroob is Chara because the name is Shruby which sounds very familiar to the name Shroob, although it is not confirmed.
- It is not yet known who replaces Mettaton, but the creator, LucasPucas, has stated multiple times that the Mettaton replacement is not Waluigi, due to large amounts of people trying to pass off Waluigi being Mettaton as canon.