"CLIMB THAT HILL"
During the episode, Laurie revealed that in the past she had sex with Richard Grieco and Charlie Sheen (as far as I know, not at the same time.) In order to cover up the truth to protect Travis' feelings, she claimed that the Richard who was still pestering her in e-mails was her Uncle Dick. (Jules revealed that Travis was so convinced that he was sending money to Uncle Dick.)
At one time, Richard Grieco looked to be the big breakout star from '21 Jump Street', but that was before Johnny Depp blasted into the stratosphere. However, his character of Dennis Booker from that show is eligible to one day be inducted into the TV Crossover Hall of Fame.
Charlie Sheen on the other hand will probably land in the TVXOHOF as a member of the League of Themselves, and just this mention of his interaction (nudge nudge wink wink) with a fictional TV character counts toward his final tally of qualifications.
They weren't the first televersions of real people to have had sex with TV characters. They join a somewhat exclusive club that also includes Roseanne, Ellen DeGeneres, and Mandy Moore.