Inside of Jabba's palace there are several scene of him that are reversed, you can tell really easily because his antena is on the wrong side of his helmet. These are shot of him casually standing against the wall in Jabba's palace, before the skiff fight, I think a few of them take place when Leia and Jabba are haggeling over a price for Chewie. It has been so long since I have seen ROTJ, I really don't remember all that well.

Be warned, if you are the type of person who is bothered by this sort of thing, forget what you have heard here today, once you notice these shots, they will likely bug you from now on everytime you watch the movie.