Taxi Driver

The script for Travis Bickle’s infamous mirror scene simply read,"Travis talks to himself in the mirror”, the rest was up to DeNiro. During filming, DeNiro dreamt up the infamous line, “You talking to me?” and thus a movie catchphrase was born.

Taxi Driver DeNiro improvised Taxi Driver's famous mirror scene

Mars Attacks

Did you think the Mars Attacks script contained a whole alien language? Well actually it contained no dialogue for the martians whatsoever. Instead it was up to actor Frank Welker to create his own alien language.

Jaws

Roy Scheider’s reaction to the sheer size of the great white shark has got to be one of cinema’s most memorable lines. But “You're going to need a bigger boat,” wasn't in the original Jaws script, that was one Scheider made up on the spot.

More: Our favourite movie easter eggs

Dr Strangelove

Peter Sellers improvised much of the dialogue in Dr Strangelove, where he took on the roles of three different characters. One unexpected moment was when the wheelchair-bound ex-Nazi Dr Strangelove, as if by magic rose from his chair and began to walk at the end of the film. Exclaiming "Mein Führer! I can walk!”, this comic moment wasn't in the script, but simply came after Sellers’ forgot’ his character wasn't able to walk.

Star Wars :The Empire Strikes Back

When you tell someone you love them the last response you probably want is an “I know”, but sadly for Princess Leia that’s all she got from Han Solo. The script actually had Han respond with the much more romantic, “I love you too”, but Harrison Ford didn't feel this fitted with Solo’s character so George Lucas allowed him to respond as he saw fit. Ford decided Hans was the kind of man to say “I know”, rather than get into anything too emotional.