As many of you pop-culture and Star Wars junkies may know, in the first SW movie (A New Hope), shortly after we meet Han Solo, he is threatened by the googly-eyed greenie Greedo, who plans on taking Han captive and handing him over to the nefarious Jabba. So what's the guy do: Act smooth and shoot the bugger.
It's believable. Han's a good guy at heart, but he's also a survivor and does what he must to get by. But when George Lucas tweaked the movie in the late '90s, he made Greedo shoot first, thus causing Han to react in self-defense. And fanboys flipped because it traded away Han's rogueish personality, and made him less believable. Even in a galaxy far, far away, certain actions make sense according to that world.