An intrepid Super Smash Bros. Brawl fan modified character models from the game to make new characters... Lots of new characters. Ones like Bayonetta, the Joker, and the cast of Dragon Ball Z.
In all likelihood, you're never going to see these characters added to the game, but it's still really cool to take a look and think about how they would play if they were.
These characters are a just a fraction of what's out there. You can check out these and many more right here.
[Via Formerly NeoGohan]