I think it would be cool if Cartman had to play the next couple of episodes with his tooth out. Wendy knocked it out and they should leave it out.
They can shoot a kid in the head and he is back next show, but if someone loses a tooth it should be permanent.
Maybe do a future show where he gets a replacement.
Also here is a link to some school pranks. What are some of your favorite ones? The show is much funnier when the show is about the kids troubles than the adults.