I'd like to praise this one for being an impressive character mod, but it is just too buggy. The "catch" mechanic works on almost anything and everything has mostly the same behavior when you do it, making it feel just like mere joke ("oh, look, I'm a butterfly jumping around", "now I became a door and went floating away"). The moves, though, are interesting and can actually be use to play the game in a different manner.
Overall, a different experience and fun for some time, until you've already used the Cappy on everything and gets tired of seeing the same joke everywhere.

Pros: laughable for some time
New moves for Mario
Catching coins with Cappy

Cons: Glitchy
Buggy
Still Super Mario 64