If movie sequels are the lifeblood that keep the wheels of Hollywood turning, prequels are often what happens when studios run out of other good ideas.
Now, that isn't to rubbish all prequels by any means, because in the sci-fi genre alone the likes of Star Trek '09, X-Men: First Class, and Rise of the Planet of the Apes have certainly proven the potential for greatness.
But more often than not, prequels end up feeling less-than compared to what came before, typically just rehashing what worked the first time for a new generation or demystifying elements of the mythology which never actually needed explaining.
Then there are these 10 sci-fi movie prequels, all of which did a sure disservice to their respective IP, whether actively dirtying the established lore, failing to deliver what audiences expected, or just lazily remaking what fans have already paid money for.
Needless to say, if you're planning a marathon of these movie franchises, don't feel obliged to watch these prequels, because there's little in the way of quality filmmaking waiting for you...