It's not easy to make a memorable horror movie monster, but something that increases your chances is making sure you have a great transformation scene.
Some sub-genres understand this all too well, and vampire, werewolf and zombie movies are all in part defined by human characters transforming into ghouls.
As a result, there's no shortage of iconic sequences to choose from for a list like this. Between the assimilations in The Thing to the rip-roaring practical effects of poor David's first full moon in American Werewolf in London, there's always going to be a bit of infighting over which is best.
However, the focus today is on the most surprising transformation scenes nobody saw coming, not necessarily the out and out best ones. These are the most brutal, grotesque and sometimes even funny times characters suddenly became more than human without warning.
One minute, you're looking at a regular old person, all fleshy parts and bone, and the next you're staring at something that'll haunt your nightmares for weeks.
10. Louise - Spring
Fellas, don't you just hate it when you meet a girl on holiday and she turns out to be a 2000-year old monster only interested in your sperm so she can have a baby and then devour its essence from inside her womb to replenish her ever-lasting youth?
Well this is exactly the situation Evan finds himself in when he meets Louise in Italy. Of course, she doesn't immediately tell him about her unique predicament (it's something you might bring up on a third or fourth date, but certainly not the first), but things get complicated when it turns out that she actually really does like him, and doesn't just want to use him as a means to an end.
Still, she's started the process, which also leaves her body in a state of flux, transforming between different mutations on a regular basis. Most of these are unseen, but one time the audience is given a quick glimpse of this painful process, where Louise is seen writhing in agony, half human and half fish monster.