Mack and PC (aka "Pervert Clown" aka "Frank Reynolds") appel, apple spoof for the FX series "It's Always Sunny in Philadelphia" -- the smartest toon about dumb-dumbs ever.
It's Always Sunny in Philadelphia's creators have a different hidden message each season which plays after the credits of each episode. The audio is just simply reversed. I've compiled seasons 1-7 (and the christmas episode) here.