One of Hollywood's worst kept secrets? Almost everyone goes by a stage name.
Don't believe us? Check out these 20 stars who adopted a fake name -- and see if you can determine what's printed on their birth certificates!
20. Bruno Mars
19. Ben Kingsley
18. Carmen Electra
17. Demi Moore
16. Elton John
15. Gene Simmons
14. George Michael
13. Helen Mirren
12. Lana Del Rey
11. Larry King
