Lord of the Rings (2001), Christopher Lee, who played Saruman, informed Peter Jackson the proper sound a man made when being stabbed in the back. His expertise stemmed from his time as an undercover agent with the British Intelligence during WWII. So, in other words, Christopher Lee was a real life, James Bond.
Monster’s Inc. (2001) is beloved by people around the world, partly because of the loveable Monsters, but, mostly because of the adorable portrayal of Boo by actress Mary Gibbs. When shooting began, Gibb was so young that she had trouble sitting still to record her lines, which lead to her having to be followed around with a microphone so the crew could then piece together pieces of the random things she would say during her play time and put it into the movie as her dialogue.
Home Alone (1990) Everyone’s favourite Christmas movie! In the scene near the end when the Wet Bandits finally catch Kevin and Hang him up on a coat hook preparing to finish him off, Harry, played by Joe Pesci threatens to bite one of Kevin’s fingers off, well guess what, during filming Joe Pesci actually bit Macaulay Culkin finger, leaving a scar that’s still visible to this day.
Titanic (1997) In one of the more iconic scenes of the movie, Jack (Leonardo Dicaprio) sketches Rose (Kate Winslet) nude while she is wearing the heart of the ocean, what you may not know is that the drawing from the movie was actually drawn by the director James Cameron
Elf (2006) During the scene where Buddy the Elf is testing Jack in Box’s, Will Ferrell’s response was genuine, Director Jon Favreau had a remote control and would decide when they would go off.