Did you know these lines were improvised?

In The One After Vegas, Rachel's line was improvised by Jennifer Aniston as her character realised the horror of what had happened...

While the pair are playing video games, David (Paul Rudd) teases Cal (Seth Rogen), saying, "know how I know you're gay?" The two came up with joke answers on the spot including: "You like the movie Maid in Manhattan" and "I saw you make a spinach dip in a loaf of sourdough bread once".

In the film, Ryan (Matt Damon) tells a deeply moving story about his family, and it was all off the cuff...

Harrison Ford's original Han Solo line to Princess Leia: “I love you too” sounded out of character, so George Lucas told Ford to just say what he thought was best. He went with a simpler “I know” which worked far better.

Okay, not exactly a line, but as the victory speech from Jim Gordon (Gary Oldman) was played out on set, actor Heath Ledger began to applaud. It was a spontaneous decision, but Christopher Nolan had his cameramen keep rolling to capture this seriously creepy moment.

That brilliant moment when psychiatrist Sean Maguire (Robin Williams) tells Will Hunting about his flatulent wife was totally improvised by Williams, and Matt Damon's hysterical laughter is genuine.

Ed's (Nick Frost) description of other customers at the Winchester to Shaun (Simon Pegg) is all improvised. Director Edgar Wright said at a film panel: "The only bit in this film that was really improvised was when you were trying to make Simon laugh."

As the janitor on Scrubs, Neil Flynn made up lots of his own material on the spot, including this hilarious scene with the excellent line: "I spent the day inside that wall, thinking I was a merman..."

Anthony Hopkins totally improvised the sucking sound he makes after describing having eaten his victim's liver. Chilling stuff...

Lloyd (Jim Carrey) asking Harry (Jeff Daniels) whether he wants to hear "the most annoying sound in the world" was improvised, and if you look at Harry's face, you can really tell...

Tom Hardy, who plays Eames, improvised the addition of the word "darling" as he pushed Arthur (Joseph Gordon-Levitt) out of the way. “The ‘darling’ part was accidental,” the actor has since said. “I came out with ‘darling’ and we kept it in because it was funny.”