Sometimes a movies does everything it says on the tin.
Take Peter Jackson's Lord of the Rings trilogy, for instance. It adapted JRR Tolkien's literary saga as faithfully as possible and kept surprise deviations to a minimum.
And that's all perfectly fine. The fans were expecting to see an epic fantasy adventure with large-scale battles, a ring-shaped McGuffin and a few Hobbits here and there, and that's exactly what Jackson delivered.
There are, however, those occasions when movies end up being two and a half hours of WTF. Times when the universe's collective expectations were way off the mark.
Sometimes this is great - a case of cinematic underdog defying the odds and reaching a level of excellence nobody thought possible, but often the reverse is true.
The films which end up nothing like fans were anticipating are usually botched adaptations or tonal misfires, the kind of abominations that twist beloved characters into unrecognisable husks, and water franchises down to the point where their essence has been drowned and the fanbase has taken up torches and pitchforks.
10. Super Mario Bros
When Rocky Morton and Annabel Jankel were hired to bring video game franchise Super Mario Bros to cinema in the early '90s, fans had no idea what to expect.
The end result, however, was something nobody could have predicted. Nintendo's twee world of mushrooms, turtle shells and bright colours became a Blade Runner-esque dystopia, and a Briton and a Latino were cast as our Italian-Americans leads.
Nothing about Super Mario Bros resembled the games, beyond the core concept of two plumbers rescuing a princess from the clutches of evil in a fantasy world.
One of its biggest deviations was casting the late Dennis Hopper as reptilian baddie King Koopa - who appears in human form for some reason - but it was the scene where Bob Hoskins's Mario plants his head between breasts of a rotund, leather-clad woman in a dino nightclub that killed every fan's childhood.
Even after a plateload of Super Mushrooms, this doesn't resemble Mario Bros.