It's just so hard to fit him into a game. He's so fourth wall-y and tends not to do well in a game that's dark or doom-and-gloom or people die a lot. Which is pretty much every game.
So that would qualify him for We The Lost, and there is also the option of confusing everyone at My Little Jamjar, by making him a pony that leaves pawprints.
Oooo, you know what? I was going to start a Star Wars game with some friends so there's no way I'd have time for two games... but Yakko in a Star Wars game would be SO. FUN.