I don't get it

Usually I like South Park. I didn't like it for years and years, thinking to was too crude. Once I started watching it (read: dating guys who watch it) it grew on me. One of the things I like most is how the show never lets you forget that the main characters are in elementary school. In one episode the boys in one class are trying to get an item from a girl and one of them suggests kicking the girl in her balls. Another boy meekly suggests, "What if girls don't have balls on the outside? What if girls' balls are up in their tummies?". That's pretty funny, Trey and Matt.
There is one South Park episode that has been on repeat that I just don't get. The kids and their parents do something that makes them hallucinate and the hallucination is that they are riding in space with a really hot woman who doesn't say anything, who takes them to her planet where everything is boobs. Houses looks like boobs, mountains, birds, weapons, all of it. It's so crass and difficult to watch. UGH.