Going off-script is common in the acting world - sometimes it's an artistic choice, sometimes it's just a matter of forgetting lines. Some of cinema and TV's greatest moments are a result of an actor's ad libbing, improvisation, completely ignoring the script, or just running with it when everything goes wrong. A good director knows when to trust his actors to go with their instinct or when to reign it in, and the best directors allow these moments to interweave seamlessly with the scripted narrative, infusing the work with a sense of authenticity.
Improv lends itself naturally to the genre of comedy (the 'You know how I know you're gay?' Knocked Up scene springs to mind), but sometimes the spark of inspiration can strike an actor during an emotional ending, or a terrifying horror scene. This list compiles just a few of the most iconic and best ad libbed moments from the hundreds that fill the movie-trivia world. Of course, moments like this that make it onto our screens are only the cream of the crop; thousands of takes have been ruined by an actor struck by a sudden moment of creativity.
10 Full Metal Jacket : Drill Sergeant
To begin with, R. Lee Ermey who played Gunnery Sergeant Hartman in Kubrick's Full Metal Jacket was just a consultant. But when the former drill sergeant and Vietnam veteran filmed his own audition tape full of improvised insults he was immediately brought on board. Ermey so completely inhabited the role that he was allowed to improvise many of his scenes in the first half of the film. At one point he was forced to explain the concept of a 'reach around' to the great director himself. Amusingly enough he went on to voice one of Pixar's characters in the Toy Story franchise.
9 Casablanca : "Here's Looking at You Kid"
Legend has it that between takes Boggart taught Ingrid Bergman how to play poker, and if these reports are to be believed it was from these moments that one of the most famous lines of all time was conceived. 'Here's Looking at You Kid' is often cited as the best improvised line, with the American Film Institute placing in 5th on its list of 100 Top Movie Quotes. However, although the line wasn't in the script, it technically wasn't improvised on the spot, which is why we've only designated it eighth place.
8 The Dark Knight : Delayed Explosion
One of the greatest, most darkly comic moments in Nolan's Batman franchise is the scene in which The Joker blows up a hospital. It was decided early on that the building's demolition would be carried out in real life, using minimal CGI to add in some broken windows. For obvious reasons this would be a costly single-take shot, with no option for mistakes.
When Ledger presses the detonator there is a small explosion, followed by a moment of confusion and much button pressing. After a few seconds a much larger explosion goes off, and Ledger runs off. Although there are no official sources verifying it, widespread rumour has it that the explosion misfired in some way, that Ledger's surprise is real, and that he improvised irritation at the scale of the first explosion to avoid the necessity of an expensive second take.
7 The Godfather : The Cat
It's unclear whose idea it was to use a cat in the scene in which Brando orders a retaliatory beating, but it is widely seen as a perfect depiction of controlled violence and a portrayal of the duality of this iconic character. Some reports have the director Coppola dumping the stray cat in the Mafioso's lap just before shooting the scene, whilst others say that Brando had found the stray himself. Whatever the case, the cat's affectionate behaviour indicates it clearly bonded with the actor, and its loud purring actually meant that several of the lines had to be re-recorded at a later stage.
6 Jaws : "You're Gonna Need a Bigger Boat"
The tongue in cheek, edge-of-your-seat 1975 thriller Jaws was the first movie to gross over $1m. It also spawned one of the most famous lines in cinema history: 'You're Gonna Need a Bigger Boat' which Roy Scheider (Chief Brody) improvised on set when the shark first appears. The oft' quoted line now places at number 35 on the AFI's list of 100 Years, 100 Movies.
5 Pretty Woman : Julia Roberts and Richard Gere
Improvisation often occurs because actors are just told to fill a space in the script, or sometimes because of a problem on set. Occasionally, a director will choose to include a moment of authentic emotion between two actors, capturing a laugh or moment of shock. One such scene occurs in the 1990 film Pretty Woman when Roberts reaches for a necklace, and in an unscripted move Gere playfully snaps shut the jewellery case. Her surprised laugh is so genuine that director Garry Marshall included it in the final cut.
4 The Dark Knight : The Clap
Whilst the explosion shows a darkly comic side to Ledger's depiction of the Joker, the scene in the prison really demonstrates the depths of his acting ability and the profound nature of his relationship with the character he depicted. In the moments following the Joker's capture, the Gotham Police Department applaud Gordon as he enters the building. The celebrations quickly peter out after the Joker begins a slow, mocking clap from behind the bars. Like the explosion, this was unscripted, but Nolan decided to run with Ledger's decision.
3 Being John Malkovich : "Think Fast"
During a scene filmed on the New Jersey Turnpike late at night John Malkovich is assaulted from a passing car. According to IMDB a drunk extra was driving past, and threw a beer can at the back of the actor's head, shouting "Hey Malkovich, think fast!" The story goes that Spike Jonze was so pleased with the results that he included the scene in the final cut, and paid the extra.
However, in a Reddit AMA Malkovich appeared to deny these rumours, saying that the scene was planned, and that when Jonze asked for volunteers to throw a can at his leading actor's head from a moving car there were over a hundred volunteers from within the crew. It is, however, very possible that the extra improvised the line to accompany the attack.
2 The Shining : "Here’s Johnny!"
As Jack Nicholson's deranged character chops his way through he door he forces his face into the hole made by his axe and screams the famous line 'Here's Johnny!' This cult moment has been used by the film's promoters ever since, despite being ad libbed on the spot. The phrase is taken from Ed McMahon's famous introduction of Johnny Carson on The Tonight Show, and was recycled by Carson himself during a later anniversary special.
In 2013 Play.com polled 10,000 users to find the ten scariest films of all time by using heart rate monitors to find when the audience's pulse was at its highest. As it turned out it was this improvised scene which took the top spot, with an elevation in heart rates of 28%.
1 Indiana Jones : Gun vs. Sword
In The Raiders of the Lost Ark there is a memorable scene featuring a whip-touting Indiana Jones confronted by some fancy swordplay from a turban-clad adversary. The crowd forms a circle around an exhausted looking Harrison Ford, and the script calls for an extended whip vs. sword fight. In a decision which would make movie trivia history Ford -who was suffering from a severe case of dysentery - abruptly takes out his pistol and shoots his opponent.
However, director Steven Spielberg didn't let Ford escape with such a light workload, and in a later instalment of the franchise this scene is alluded to when Indy reaches for his holster, only to find that his gun is missing.