Mario and Sonic: Adventure 3D
An RPG about the colision of Mario's World, and Sonic's World, where Silver comes from the future to stop the universe from seizing to exist, because of an event so bad, that even traveling to the past won't stop the clock from ticking, with a plot to collect Chaos Emeralds, Sol Emeralds, Grand Stars, 40 Power Stars, Five Powerful Rings, The Star Rod, and the Access Oras (Nintendo & Sega Accesory parodies redesigened for a more serious & still ironic tone)
Villians include
Eggman
Eggman Nega
Gerald Robotnik
Metal Sonic
Solaris
Ultimate Negative Chaos
Bowser
Dry Bowser
Robot Bowser
Shroob Army
Tatanga
Galactic Mario
Shadow Queen
King K. Rool
Tabuu
Playable Characters at various points
Mario
Luigi
Wario
Waluigi
Peach
Daisy
DK
Yoshi
Sonic
Tails
Knuckles
Amy
Shadow
Rouge
Blaze
Silver
AiAi
NiGHTS
Other Sega Characters
Kirby
Meta Knight
Tiny Olimar (about the size of character's Foot)
Captain Falcon
Square Enix Characters
Mii (customized character for main character from "another world")