UAF:Backstory
Various people from different multiverses and dimensions create a fighter federation known as UAF(Ultimate Apex of Fighters) that all fighters from every dimension fighting for championships as well as for the fame and money aspect of it. Also there are 3 brands in this federation: MCF(Meta Combat Federation), SMC(Superb Multiverse Combat) and PFC(Professional Fighter Combat).
Sidenote: Still trying to figure out which series I should include in this first. It will include any cartoon character, any video game character, basically any animated character.