The Great Battle

Everything happens in a flat place; the ground is made of smooth, soft rock, and 20 trios appear (one of which consists of 4 people, but that's an exception).
First trio: Mordecai, Gumball, and Finn
second trio, Rex, Max Steel and Ben 10 (Alien X)
Third trio: KORobin and Samurai Jack
Fourth trio: Clarence, Uncle Grandpa (Toon Force and fanny pack), and Steven Universe (Steven in pink form).
fifth trio: Johnny Bravo, Dexter and Buttercup (but she's with Blossom and Bubbles)
sixth trio: Chowder, Lazlo and Oggy
seventh trio: mac, flapjaco and Edu (along with Dudu and Du)
Eighth trio: Lance, Eli Shane, and Super Robotboy
Ninth trio: Courage the dog, Scooby-Doo, and the polar bear (along with the panda and the grizzly).
Tenth trio: Woody Woodpecker (Toon Force), Tom and Jerry (Toon Force), and Bugs Bunny (Toon Force)
Eleventh trio: Tromba Trem, Monica and Jorel
Twelfth trio: Juniper Lee, Omi, and Static Shock
Thirteenth trio: Felix (Toon Force), Pink Panther (Toon Force), and Popeye (Toon Force)
fourteenth trio: mao mao, Tulio Olsen and Wirt
fifteenth trio: Pure bone, Johnny test and nigel uno
sixteenth: Cole, Zane, Jay and Kai
Seventeenth trio (villains): Voltar, Zs'Skayr, and Albedo
eighteenth villainous trio: lich, lemongrab and ice king
nineteenth villainous trio: antipairulito, abu and rob
twentieth villain trio: white diamond, Slade, and Benedict Uno
You can be whoever you want, they are ready to fight in an epic and probably long battle.