Here's another entertaining theory that The Beatles were actually Klaatu, and that John Lennon assumed the identity of Tony Sheridan.
http://invanddis.proboards.com.....nnon-alive
These theories are all discussed on various message boards. I love the ones where they take different photos of The Beatles and show how their faces are different--John's jawline is rounded here, square there, so this one is the impostor, etc.