2. Darth Vader/ Anakin Skywalker
Back in the late 70s, a whole generation of children waited in line to Star Wars, and in that they saw possibly the most Awesome Villain of All Time. Decked out all in black and wearing a mask that was one part skeleton, one part nazi helmet, he was the epitome of evil. He also had cool powers (he could crush the throats of British TV actors without using his hands), his own little ship, and even an evil red version of the hero's special sword. A couple of years later, the audience was a bit older, and they found out that Darth Vader was actually the dad of the film's hero. Which was sort of, well, weird, wasn't it? Then, in the third movie, the mask came off Vader: turns out he was just a smiling old man with a bald head and bad skin. Who dies. It wasn't really his fault, though. He wasn't an idiot. Not at that point. Turns out he *used* to be an idiot, only we didn't know it, because George Lucas hadn't made prequel movies yet. A generation later - when that original audience had children of their own, ready to be indoctrinated into the magic of the movies - another trio of films came out, this time explaining who Darth Vader REALLY was, from petulant slave-child moppet to stroppy teen Anakin. Worse yet, he was so damn annoying. The one saving grace - if you watch them in the 'proper' order (that is, starting with The Phantom Menace and ending with Return of the Jedi), you at least get to see Vader finish off the guy who made such an idiot out of him in the first place. (Lucas actually spoiled even that scene in the recent Blu-Ray release of the original trilogy). That original audience who'd grown up with Star Wars found out a quarter of a century later what an idiot Darth Vader really was - and in doing so, many a childhood memory was sullied.