Scientology is a particularly exotic delusion.
To be perfectly frank, I've seen equally exotic and entertaining delusions described on this forum and just about everywhere else I encounter people.
The funniest, and in some ways most harmful, is our persistent delusion that each of us is a completely separate, self contained ego encapsulated within a bag of skin that is somehow independent of the earth and the rest of the universe. That's a real hoot and gives us the excuse we need to perpetuate all kinds of terrorism on one another and the environment... Nevertheless, it's very convincing and is unlikely to change anytime soon on the large scale...