No, you're not seeing things. On an episode of The Simpsons called Duffless, Larry the Barfly is shown twice in the same scene:
That's him wearing two different colored shirts commiserating with both Barney in the foreground and Sam in the background. Chances are, the animators were told to include pictures of random drunks in the background and didn't realize they drew the same character twice.
(special thanks to our special correspondent Max Vasquez for submitting this crazy animation error)
