Okay, so I got a little confused at the end. Did you call a waitress a bitch and/or break a plate? Or did the other guy tell the boss that when you actually didn't?

If he fired you just for messing around it's a little harsh. What's he expect you to do when there's no dishes to be washed - just stand and stare at the empty sink / dishwasher? But then it depends on whether you could be seen / heard from the restaurant floor. If that's all you did, try explaining to the guy that it was the girl who decided to flash you, and you didn't do any of the other things.

If, on the other hand, you did do those things, well I guess I can see where he's coming from. It's not gonna be hard for him to find another dishwasher, like Mingles said, and maybe that one won't give him problems.

Either way, if you considered the other guy a kinda-friend it's bad form for him to have snitched on you to the boss, but is it really worth getting into anything over a dishwashing job? Yeah, it sucks that you've now got to look for another position, but it's not the end of the world.