1.The classic "What are you waiting for?" line in I Know What You Did Last Summer was suggested and directed by a child who'd won a contest to create a moment in the film.
3.The scene in Mrs. Doubtfire where Daniel sticks his face in a cake to avoid being recognized was planned — but the crew didn't realize the heat from the lighting would melt the frosting, causing it to fall into Mrs. Sellner's tea.
4.Nathan Lane, who voiced Timon in The Lion King,ad-libbed the line, "What do you want me to do? Dress in drag and do the hula?" They then added a scene of Timon doing just that.
5.The oft-thirsted-over scene in which James Bond walks out of the water in Casino Royaleonly occurred because Daniel Craig hit a sand bank.
6.Dustin Hoffman actually farted in the phone booth scene in Rain Man, and Tom Cruise's reactions were improvised.
7.The "Hi, doggie" line in The Room was from Tommy Wiseau genuinely noticing the dog for the first time in the scene.
8.The Children of Men scene when blood splatters on the camera was a complete accident — it happened on their last chance to film the six-minute continuous scene.
9.Mia falling on the bleachers in The Princess Diaries was totally unscripted — Anne Hathaway really did accidentally fall, as it had just rained and the bleachers were slippery.
10.Kat wasn't supposed to start crying during her speech in 10 Things I Hate About You, but Julia Stiles started crying in the take, and they liked it so much they didn't shoot it again.
11.The "she talks in her sleep" line in Indiana Jones and the Last Crusade was improvised by Sean Connery.
12.The incredible "He's a friend from work" line in Thor: Ragnarokwas suggested by a kid — a Make-a-Wish recipient who was visiting the set.
13.The Joker scene when Arthur dances in the bathroom was improvised: he was just supposed to hide the gun and wash his face.
14.The "Old Time Rock & Roll" dance scene in Risky Business was also largely improvised by Tom Cruise.
16.Leonardo DiCaprio accidentally cut his hand while filming his famous Django Unchained rant, and chose not to react and just continue with the scene with a bloody hand. The take ended up in the film.
17.And finally, that super-awkward yet memorable Voldemort/Draco hug from Harry Potter and the Deathly Hallows — Part IIwas improvised.