I have to admit I was pretty sceptical about Finding Dory. Pixar's been hit-and-miss for a while now and the company's directors haven't been shy about the new wave of sequels (the next three years will see new entries from Cars, Toy Story and The Incredibles) being a corporately-mandated move (Dory is pretty much Andrew Stanton's apology to Disney for John Carter anyway). But my biggest problem was taking a supporting character from the original and bumping her up to the lead - that's a risky move.
Did it work? Well, kinda. We got to have a semi-repeat of the original film, but the new perspective made it fresh and added an underlying message about living with disabilities. But at the same time, the original characters you fell in love with, Marlin and Nemo, were sidelined to a cute-but-pointless subplot and their replacement didn't quite warrant Dory's expansion.
Of course, that's better than some cases. The trick of swapping out a main character is a staple of franchise cinema born out of necessity; actors don't want to return, a side character becomes a break-out hit or a new writer finds themselves taking the series in a new direction. Now it can work really well - Terminator 2: Judgement Day seems like the obvious one, although you can also rope in the likes of The Force Awakens too - but just as often can ruin what made the original so special. Here's ten of the dumbest examples.