People here are strongly implying I'm ONLY using Diddy in Brawl. Which is not the case.
In Brawl I use: Diddy, DK, Ike, Link, Ganondorf, Sheik, Marth, Pikachu, Samus, Yoshi,Ness and Pokémon Trainer. Could probably also kick your ass with Bowser, Captain Falcon, Jigglypuff and Mario on a good day.
In Melee: DK, Mewtwo, Jigglypuff, Samus, Sheik, Link, Mario, Marth and Ganondorf.
In 64: I basically only use Pikachu, DK and a little bit of Link.
So no, I don't only play Smash for Diddy, but I'd be outraged if he wasn't in Brawl nonetheless. I also use characters mostly from series that interesst me most, and I'm far more inclined to learn a character I like than otherwise. And if their playstyle suits, I'll stick with them.
To be honest, I think I was far more 'relligious' about Pikachu in 64 and Mewtwo in Melee for a long time than I was about Diddy in Brawl. However, I'm probably the best with Diddy still all around.
But yeah, hate me for it if you like. I don't care anyway.