I really like Mad T Party and the threads linked in the previous post will give you a pretty good sense of what it's like.
When are you going? It's worth noting that right now they're doing a semi-Halloween Themed Mad T Party, so it's a little different. It's worth going to the last set (one hour before park closing). During the holiday season, they do a Holiday-themed Mad T Party. Basically, they're perform a few holiday songs.