There are two additional scenes that are not included in the special edition. The first one is near the beginning when Han is asking if Luke has made it back, you will notice that there is a slaughtered Taun-Taun on the ground. In the scene they discuss that something has killed it. Later, the Ice Creatures attack the Hoth base and get locked in a storeroom. A sticker is placed on the door saying do not open. In some of the promotional materials there is a shot of C3PO peeling off the sticker. Stormtroopers open the door and get killed. When Vader enters the base, he asks 'What killed these men?' After all, they had to blast into the room, and it's already full of dead Stormtroopers.
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)
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."
Frank Oz's performance as Yoda impressed George Lucas so much, Lucas spent thousands of dollars on a campaign to nominate Oz for a Best Supporting Actor Oscar. However, the Academy shot this down, feeling that puppeteers are not "actors."
This is in the Special Edition of The Empire Strikes Back. Darth Vader returns to his Star Destroyer (just after the Millennium Falcon retrieves Luke from underneath Cloud City). The shot that is used to show Vader walking down the shuttle ramp and into the Shuttle Bay is from Return of the Jedi (different angle) when he enters the Death Star at the beginning. You can see Moff Jerjerod just before the end of the shot.
While filming the scene in which Yoda and Obi-Wan try to convince Luke not to leave Dagobah, Mark Hamill was accidentally bitten by a snake he pulled out of the X-Wing's thrust engine.
During the chase in the asteroid field, a TIE fighter is hit by a little one. If you watch in slow-motion, you can see the pilot ejected from the explosion.
When Darth Vader is addressing the bounty hunters, next to Boba Fett is IG-88, the bounty hunter from "Shadows of the Empire".
This is the only movie in the Star Wars series which doesn't have a scene on the planet Tattooine.