I have always been a really big fan of the series so this was a real enjoyable movie for me. I think though even if u don't watch the show or haven't seen it this movie will still be funny. The content is iffy but it's only references, and most kids won't get it in the first place. So all in all great movie for 12 and up.
The series was always funny, and the movies follow after. This movie was not as bad as the last movie, but still contains some innapropriate material I say it really depends on how mature your kid is, not how old he is.