Elvis didn’t do no drugs means in slang: A term used to refer to someone who is telling a lie, pretense or falsehood. An expression that refers to bullshit. It is well-known that Elvis used a lot of drugs. Therefore, it would seem like bullshit to claim that he was always clean. Origin: Penn and Teller’s Bullshit. This is where bullshit was used for creationist claims.
(in Slang Dictionary, added by Feliciano Carmona)