If you want to see the episode that started the current controversy with South Park and Scientology, you can watch the whole thing for free here.
I have written here before about not being a huge fan of making fun of religion, but in all seriousness, Scientology isn't a religion; it's a scam.
The episode is about 23 minutes long. Oh, and be prepared to laugh. A lot. But only if you think making fun of Tom Cruise is funny. Which you should.