John Waters, one of the most interesting and line-pushing talents in Hollywood, joked on “Real Time” Friday night that he’s become so respectable, he wants to gag!

Waters was hysterical with Bill Maher, pitching his new book, “Liarmouth: A Feel-Bad Romance.” For the uninitiated, Waters wrote, directed and/or produced some of the most out-there movies in history, including “Hairspray,” “Serial Mom” and “Pink Flamingos.”

It’s pretty incredible … John says the National Registry has named “Pink Flamingos” — a movie where the main character eats a dump for all to see — one of the great American films. Fact is … it’s a fantastic flick, and this year marks its 50th anniversary.

The Motion Picture Academy has created an exhibition around Waters’ works. He says he’s looking for something Divine — the enduring character he created — wore … a “cheater.” A cheater, for those who don’t know, is a contraption with fake pubic hair. He’s on the hunt for someone who has it, and would love to put it in the exhibition near Dorothy‘s ruby red slippers!!!