Revealing mistake: When the Falcon leaves Hoth and is being chased by the Empire, there is a scene where the ship gets rocked about. During the 'impact', C-3PO's arm becomes dislodged, and you can clearly see human skin underneath. (00:36:20)
Trivia: The Special Edition covers of Return of the Jedi and Empire Strikes Back are wrong. The picture of the Emperor on ESB cover is from 'ROTJ', and the lightsaber duel between Luke and Vader on the cover of ROTJ is taken from 'ESB' (notice Luke is in his fighter pilot suit, and Vader is fighting him one-handed)
Trivia: There was a false page in the original script in order to fool all of the people working on the film. This was to keep it secret that Darth Vader was Luke's father. Only George Lucas, the producers and James Earl Jones knew the truth. Mark Hamill was told just moments before filming this scene so his reaction would be right, while David Prowse read the lines from the original script "Obi-Wan killed your father."