The name is originally titled Revenge of the Jedi in both posters and even the teaser trailer before Lucas changed the title a few weeks before the premier (as Jedi do not seek Revenge).
David Lynch turned down George Lucas's request for him to direct Return of the Jedi. Before approaching Lynch, Lucas wanted Steven Spielberg to direct, but because Lucas was no longer part of the Director's Guild, he couldn't get him.
The original plan for "native allies on Endor" was not Ewoks, but instead a band of escaped Wookiee slaves. But Lucas wanted the battle to be fought "old school" with bows and arrows and Wookiee's had advanced technology. So he decided to "Cut them in half and call them Ewoks." Also, Kenny Baker (the little guy who was inside R2 making him shake) was supposed to play Wicket but he fell sick for most of the production and that's when Warwick Davis stepped into the role.
The script described a little more detail about Luke and Leia's mother. She was disguised as Leia's adoptive parents' maidens. She died when Leia is about 4. This was partially canon until Episode III.
There was an early script where The Falcondoesn't Outrun the Fireball and gets destroyed along with the Death Star II.
Prior to the making of the film, Mark Hamill speculated that it would have involved Luke turning to the dark side, with the main conflict being generated by whether or not he'll be turned back. A similar plot thread eventually re-emerged in the Dark Empire serial.
Originally Moff Jerjerrod, the sort-of whiny overseer of the Death Star's construction, was written as Grand Moff Jerjerrod, and was Palpatine's personal representative, and schemed with him to turn Luke and betray Vader. When Vader finds out he breaks Jerjerrod's neck. From this important role he was reduced to just another Imperial flunkey with on a minor connection to the Emperor.
Creator Cameo: Director Richard Marquand portrays a rebel pilot and voices one of the evil droids in Jabba's palace
