SFX crew claim to have included a "sneaker" as one of the spaceships in a complex dog-fight scene.

     Jabba's sail barge was filmed in Yuma, Arizona. The film crew had problems avoiding the 35,000 dune buggy enthusiasts
     in the area. To preserve secrecy, the producers claimed to be making a horror film called "Blue Harvest (Horror beyond
     your imagination)", and even had caps and t-shirts made up for the crew. A chain-link fence and a 24-hour security
     service could not prevent die-hard fans from entering the set and sneaking some photographs.

     Luke's hand gets shot. Leia gets shot in the shoulder. Luke cuts off Darth Vader's hand. See also Star Wars (1977) and
     Empire Strikes Back, The (1980).

     The main chamber of Jabba's palace is connected to the entrance by a short flight of steps. When filming the scene
     where R2-D2 enters the chamber it was discovered that the droid could not roll down the stairs. In the movie we see
     R2-D2 approaching the stairs, then the camera moves to the left past the steps and the droid re-enters the field of view,
     having been manually hauled down the stairs.

     The dancer that Jabba drops into the Rancor pit loses her top as she falls in.

     Carrie Fisher's birthmark (near the small of her back) is visible in the desert scene where she turns her back to the
     camera to swing around a mounted laser gun.

     Rumour has it that Nien Numb speaks a Kenyan dialect, and one of his lines is "One thousand herds of elephants are
     standing on my foot".

     Lando Calrissian and The Millennium Falcon originally scripted to perish in the Death Star explosion, but this was
     changed after a poor preview audience reception. Note Han's line when Calrissian leaves in the Falcon: "...like I'm not
     going to see her again..."

     It is rumoured that a different ending was shot, but discarded later on. It featured the (long awaited) marriage between
     Leia Organa and Han Solo. Dark Horse's Comic "Dark Empire" is based on that fact and presents Han and Leia as a
     married couple.

     Denis Lawson, who played Wedge Antilles in Star Wars (1977) and Empire Strikes Back, The (1980) plays Wedge in
     this film, despite the rumours to the contrary which were caused by his name being misspelt ("Dennis Lawson") in the
     credits of Star Wars (1977). Intense debate on Usenet prompted Jarod Nash to write a letter to Lawson, asking for
     clarification. Lawson confirmed that he indeed played in all three movies.

     Among the aliens in Jabba the Hutt's entourage are ones named "Klaatu," "Barada" and "Nikto," after the command
     given to the robot Gort in Day the Earth Stood Still, The (1951). The aliens are not referred to by name in the film, nor
     do they have any lines. Klaatu is the character who tries to push Luke into Sarlacc.

     The name "Ewok" is never used to refer to the teddy-bear creatures in the film, though it does appear in the credits.

     The following characters "have a bad feeling about this": C-3PO, Han, and Lando.

     The Endor shots were filmed near Crescent City, California. Forest work was especially hard on the Ewok actors.
     Production Assistant Ian Bryce arrived on the set one day to find a note from the Ewok actors saying that they had all
     had enough and they were on their way to the airport. Bryce tried to drive to the airport, but got a flat tire not far from
     the set. He found another car and was about to leave when the Ewoks' bus pulled up, and all the Ewok actors got off
     wearing "Revenge of the Ewok" t-shirts.

     Darth Vader's body was played by David Prowse, his voice by James Earl Jones, and his face by Sebastian Shaw.

     One of the songs that the Ewoks sing sounds like: "Det luktar flingor har", which is Swedish for "It smells of cereal here."
     Another song sounds identical to a song sung in Caveman (1981).

     The title "Revenge of the Jedi" was leaked early in production, so that pirated merchandise could be easily spotted when
     the film was released. The official reason for the change was that "...a Jedi would not take revenge". Some authentic
     pre-release movie posters actually had "Revenge", and are worth a lot of money today.

     Portions of the partially completed Death Star model resemble the San Francisco skyline.
 

Source from IMDB