The original Star Wars trilogy had a very distinctive beginning, middle, and end. How do you write about Luke Skywalker and keep it interesting when he's already saved Vader and crippled the Galactic Empire? Easy. You make up a sh*tload of characters and undo everything that made the series great. Here's our tribute to the Expanded Universe's biggest crimes against the franchise.
In The Movies: Vader's character arc crystallizes in a single moment. Inspired by his son's goodness and faith in him, Vader picks up the Emperor, the personification of corruption in both himself and the galaxy, and throws him into a conveniently-located bottomless shaft. That thing was just a lawsuit waiting to happen.
In The Expanded Universe: But wait
what was that about clones? Ah, that's right. It turns out the Emperor has a whole ship full of younger hims, just waiting to spring into action if the old him ever died. (Why did he bother hanging out in that crippled old body in the first place? We don't know, but Space Viagra must be super effective.) Vader's final sacrifice, his ultimate act of defiance, now comes off as a minor annoyance. He might as well have stepped on the Emperor's robe while he was walking down the stairs.
In The Movies: There are two sides to the force. The Light Side practices compassion and mercy, while the Dark Side feeds on anger and fear. The Dark Side is a constant temptation for Jedi, since it encourages raw emotion over patience. It's addictive, and corruptive to the point that it can alter a Jedi physically.
In The Expanded Universe: The Force is neutral. There is no alluring Dark Side, just evil people that use the Force for evil things. On the surface, this seems like a decent enough explanation. Jedi who turn to the Dark Side often have motives besides merely being "seduced." Still, to deny that the Dark Side has some sort of alluring power makes you wonder why something like one out of every four Jedi turns to the dark side. Can you think of any other story where 25% of "good" characters end up becoming total bastards?
In The Movies: Obi-Wan is thought to be the only living Jedi until it's revealed that there's an ancient Jedi Master named Yoda that Luke must seek out. After Obi-Wan is killed, Yoda says to Luke, "When gone am I
the last of the Jedi will you be." He croaks and Luke is alone in his Jedi-dom.
In The Expanded Universe: Not only did a shit ton of Jedi survive Order 66, but there's a laundry list that were still alive throughout the course of the entire original trilogy. Sure, ol' Ben and Yoda can't be expected to know every force-sensitive hermit that goes into hiding, but the expanded universe introduces a gaggle of Jedi actively participating in the rebellion. Why stay true to the source material when you can write new stories about cool guys with lightsabers!?