The first part of Mario and Sonic the Ultimate Crossover was uploaded on June 16th 2016 to unoffically celebrate the 25th anniversary of Sonic the Hedgehog and 35th anniversary of Super Mario.
The story begins in the Sonic universe where Knuckles comes to warn Sonic about Dr Eggman and what's he going to do. Sonic tells Knuckles and Tails that they're on thier way to rescue Amy Rose and Cream the Rabbit from Eggman.
Eggman demands Sonic to hand over the Chaos Emeralds in exchange for Amy's safety
- This is the only part to not feature Luigi, Yoshi, Daisy Toad, Donkey Kong, Diddy Kong, King K Rool, Geno, Shadow, Rouge and Big the Cat. They will appear in the next part.
- Wario and Waluigi are the first Mario characters to arrive in another universe.