You have some good advice below, but I would also add that many cartoons are heavy on the body humor -- farting, ripped pants, showing underwear, etc. There's often a big focus on butts! You might want to check out his TV diet (just 'cause it's for kids, doesn't mean it's good for kids) and see if you need to make any changes. Some "clean" programming you could look for -- Between the Lions (PBS), VeggieTales videos (check the library), Thomas the Tank Engine (again, check library & also TV listings). Those are a few. Watch out for shows like Sponge Bob Square Pants (there's even a whole show about ripped pants/butts), Rugrats, Simpsons, etc.
I wish you the best.