Whilst most of the time it is best to stick to the script, sometimes letting performers do their thing yields even better results. Improvisation is a real skill which not too many master, but when they do it can have an enormous impact on the entire scene and consequently the entire film. Some of the most iconic moments in cinema history were completely improvised, and although the writers may not be best pleased, it lifted the whole film and created some unforgettable moments. Here are 10 instances where performers got creative and went off script, resulting in some fantastic scenes.

**Warning: Some of these scenes have NSFW language**

10. Dumb and Dumber

Jim Carrey is such a ball of energy that he frequently goes off script in his films, and often this results in material that is funnier than what was scripted. In 1994’s Dumb and Dumber, the scene where his character, Lloyd Christmas, and Jeff Daniels’ character, Harry Dunne, pick up a hitchhiker is all completely improvised. In the film, the hitchhiker, Joe Mentalino (Mike Starr), they pick up is actually a hitman who is hired to kill them, but their antics are almost unbearably irritating as he sits in the middle of them. He momentarily manages to calm them down, before they ask if he wants to hear the most annoying sound in the world. Originally, the script had them arguing about Jelly Beans but the two actors went in a new, and very funny, direction with the scene which perfectly captures how annoying they can be.

9. Jaws

Much of the dialogue in Steven Spielberg’s 1975 horror/thriller classic Jaws was created on the set, with scripts typically being written for scenes just the night before they were shot. One of the most notable lines that was created on set came from Roy Scheider, who plays Chief Martin Brody. Whilst attempting to lure the great white shark within range, Brody gets his first proper look at the killer beast which fills him with fear. He then turns to Orca Captain Quint (Robert Shaw) and says “you’re gonna need a bigger boat.” This fantastic line was completely improvised, but brilliantly struck fear in both the characters and the audience as they realize just how enormous the shark is. It is such a great line, that people often now say “you’re gonna need a bigger X,” and this is all thanks to Roy Scheider.

8. Star Wars: The Empire Strikes Back

In one of the great Star Wars moments, Harrison Ford’s Han Solo lived up to his rogue persona by simply replying “I know” when Princess Leia (Carrie Fisher) declares her love for him. She cries out “I love you” as he is about to be encased in carbonite, and he was originally supposed to reply with “I love you too.” However, after several takes where it did not feel right, Ford felt that the characterization was all wrong and director Irvin Kershner told him to just do what felt right. Ford nailed it with his “I know” response, which excellently captured the essence of his character and avoided him showing too much compassion. It is also one of the more memorable exchanges of dialogue in the entire franchise, but be careful if you use this response to a loved one as it could land you in trouble.

7. Midnight Cowboy

Nowadays, whenever anybody is impersonating somebody from New York, there is a good chance that it will include the phrase “I’m walkin’ here!” This comes from 1969’s Midnight Cowboy and is delivered by Dustin Hoffman’s Ratso as he and Joe Buck (John Voight) are walking down the street. They almost get hit by a yellow cab, to which he bangs the hood and delivers the classic line. The story behind the line is a fascinating one, and Hoffman explained that there were many takes to get the traffic just right as they crossed the road so that they did not have to pause whilst walking. The timing was perfect in this take, but a cab came out of nowhere and nearly crashed into them. Hoffman managed to stay in character and not ruin the take, despite almost being hit, and delivered one of the most quoted film lines ever.

6. A Clockwork Orange

At the start of Stanley Kubrick’s A Clockwork Orange, we are introduced to Alex DeLarge (Malcolm McDowell) and his gang as they engage in horrible “ultraviolence.” This includes the raping of Mary Alexander (Adrienne Corri), to which they shockingly sing “Singing in the Rain.” The scene was shot several times prior to this but Kubrick was not happy with it, which saw him suggest to McDowell that he did whatever he wanted to add something to the scene. This song is what he chose, which results in a haunting moment and also one which caused plenty of backlash from the British press with Kubrick’s family receiving threats. Corri also was not happy with how many takes it took and how long the scene lasted, and there was originally an actress cast before her who quit due to the difficulty of the scene.

5. The Godfather

These days, all good villains need a cat to stroke whilst they explain their master plan. This all stemmed from the iconic scene from Francis Ford Coppola’s 1972 masterpiece The Godfather. Surprisingly, the appearance of the cat that Vito Corleone (Marlon Brando) strokes as he sentences a man to be beaten was not in the script. The story goes that the cat would always be hanging around the studio, and moments before they shot this iconic scene Coppola simply dropped the cat into Brando’s lap. This helps to emphasize just how cold-hearted he is, as he shows no emotion as he condemns this man and casually strokes a cat whilst he does so. It turned out to be such a fantastic scene, that it has been parodied countless times and cats have become popular accessories for many evil characters in spy and action films.

4. Good Will Hunting

The master of improvisation, Robin Williams was famed for going off script and leaving the cast and crew in hysterics in many of his films. The greatest moment came in Matt Damon and Ben Affleck’s Good Will Hunting (directed by Gus Van Sant), where Williams plays the unforgettable and touching role of therapist Sean Maguire (earning him an Oscar for Best Supporting Actor). In one fantastic and important scene, Sean tells Will Hunting (Damon) a personal story in a bid to make a connection and encourage him to open up. The story is a hilarious one about his late wife, who would wake herself up with her flatulence. Damon’s hysterics are genuine, and if you look closely you can even notice that the camera is shaking from where the cameraman is laughing too. Simultaneously hilarious, touching and important, it is a key moment and Williams at his very best.

3. The Silence of the Lambs

Anthony Hopkins turned in an incredible performance as Dr. Hannibal Lecter in Jonathan Demme’s The Silence of the Lambs (and Hannibal), which rightfully won him Best Actor despite him having less than 20 minutes of screen time. You simply cannot take your eyes off of him for a second, and he is as intriguing as he is terrifying. In perhaps the most shocking and iconic moment, he tells FBI agent Clarice Starling (Jodie Foster) a story about eating a census taker’s liver “with some fava beans and a nice Chianti,” before making a skin crawling hissing sound which startles Clarice. This sound that he makes was not scripted, but it was something that Hopkins did during rehearsals to try and freak Foster out. Additionally, Hopkins also improvised the moment where mocks her Southern accent which shocked Foster and was important in terms of the power balance between the characters.

2. Taxi Driver

Another one of the most famous lines ever delivered in cinema was again completely improvised. In Martin Scorcese’s legendary Taxi Driver, the sociopathic and insomnia-plagued Travis Bickle (Robert De Niro) has an imaginary confrontation whilst looking in the mirror where he repeatedly says “you talkin’ to me?” before drawing his gun. The script only says “Travis talks to himself in the mirror,” so it was all De Niro’s brilliant creation. It has become such an iconic and replicated quote, both in society and cinema, that it was voted number 10 on the AFI’s “100 years…100 movie quotes” list. The line shows just how much Bickle is spiraling out of control, and also shows the character’s need to mimic the social interactions that he sees around him, but does not participate in. Forty years on, it is still a line that people say to themselves in the mirror.

1. The Shining

There are few lines as iconic as “here’s Johnny!” from Stanley Kubrick’s adaptation of Stephen King’s The Shining, and it is a line that is still highly quoted today. The line, delivered by Jack Nicholson’s disturbed Jack Torrence as he chops down the door with an axe, is chilling as it shows just how deranged he has become and the delivery is superb from Nicholson. The line came from Ed McMahon and was his catchphrase introducing Johnny Carson on The Tonight Show Starring Johnny Carson, and this unthreatening origin makes it only more chilling. The line was not a part of Kubrick’s original script, and instead was completely improvised by Nicholson. The take almost was not used as Kubrick was not aware of the significance of the line as he had lived in England for a long time, but fortunately he soon realized just how affective it was.