According to some Scientologists, and I'm not one, nor do I play one on TV, and to the best of my knowledge, Xenu is a space alien, representative of the many space aliens which inhabit human bodies. They are bad naughty space aliens.
Apparently it is the job of a Scientologist auditor to help other humans to rid themselves of space aliens.
If you join the Church of Scientology, pay a lot of money and go through many auditing sessions (around $400/hour and up) eventually you will reach a level where you will have a clearer understanding of Xenu. They might even let you shake hands with Tom Cruise.
ROTFLMAO!!!
P.T. Barnum would have been awestruck at this.....the sheer marketing brilliance of it all.
My guess, however, is that Barnum respected people's intelligence too much to even consider the notion of anyone falling for a stunt like this.