9. The Dragon Firework - The Lord Of The Rings: The Fellowship Of The Ring
By this point everybody knows that Viggo Mortensen broke his toes after kicking a metal Uruk-Hai helmet during filming for The Lord Of The Rings: The Two Towers, but while shooting The Fellowship of the Ring, Pippin actor Billy Boyd got quite the gnarly surprise himself.
During filming for the famous scene where Pippin and Merry (Dominic Monaghan) steal one of Gandalf's (Ian McKellen) dragon fireworks on Bilbo's (Ian Holm) birthday, Boyd apparently didn't get the memo for how the scene would be executed.
And so, he had no idea that the firework would actually fire into the sky while he was in front of it, ensuring that his hilariously high-pitched, terrified scream is actually completely genuine - as Boyd himself confirmed on the film's DVD commentary.
The terror, as amusing as it was, was totally real.