2. Midichlorians - Star Wars Episode I: The Phantom Menace
This is simply another case of a prequel that explains far too much, and in this stead, ruins the perfectly palatable mystique of what was previously established. The original trilogy made it clear that The Force was an esoteric form of energy that allowed people to be totally kick-ass, and we didn't need to know anything more; we accepted this. Episode I, however, made pains to explain what The Force actually is, with Lucas introducing the concept of Midi-Chlorians, micro-organisms which dictate how much Force power one has, and those lucky enough to be Sith or Jedi simply have an extraordinarily high Midi-Chlorian count compared to regular folk. All Lucas has done is give a flimsy explanation to something that didn't need it, and the fact that he opted to give it such a silly name only compounds the problem. Episode I was already teetering on the edge, but this just made me outright despise it.