LOUIS C.K. told a joke during a 2009 interview that has come back to kind of bite him in the ass.


He was making fun of audience members on "Inside the Actors Studio" who ask questions . . . and said they were NEVER going to become famous.


He said, quote, "When an actor stands up . . . and asks SEAN PENN or whoever, 'What can I do to reach your level?' . . . you just wanna say, that's it, you never will be famous . . . There's no way you ask Sean Penn a question and then you're gonna be huge."


But in 1999, 10 years before he told the joke, Sean Penn WAS a guest on "Inside the Actors Studio".  And one of the aspiring actors who asked him a question was . . . BRADLEY COOPER.