Famous movies wouldn’t be anything without their most recognizable scenes. But did you know that many iconic moments of cinema weren’t originally written into their scripts? Instead, the actors got creative and added their own personal spin to their performances.

It might seem shocking that Casablanca’s romantic ending came about on a whim, or that Jack Dawson’s catchphrase “I’m the king of the world!” was made up on the fly. But creativity often thrives under pressure, and these movies are all the better for their last-minute changes.

Here are 12 celebrated movie moments that were improvised during filming.

  • 1

    Napoleon Dynamite — Napoleon’s Big Dance Number

    The climax of Jared Hess’ quirky Napoleon Dynamite comes towards the end, where an empowered Napoleon (Jon Heder) performs a rousing dance to Jamiroquai’s “Canned Heat,” capping off his friend Pedro’s lackluster campaign speech for school president. As it turns out, the dance scene was completely freestyled by Heder. Hess knew of Heder’s passion for dancing, but originally didn’t feel it had a place in the movie. But once he saw Heder’s amazing moves to the funky song, he knew it had to be the movie’s big finish. On the day of filming, Heder improvised the dance routine on the spot. After three takes, his spontaneous moves were stitched together to create the glorious sequence we see in the final film.

  • 2

    Jaws — “You’re Gonna Need A Bigger Boat”

    This line from Jaws has become ubiquitous — even if you haven’t seen the movie, you’ve probably heard it somewhere. Which is funny, considering it wasn’t even in the original screenplay. It started out as an on-set joke between the cast and crew, referencing the production team’s too-small boat. But then, actor Roy Schneider decided to incorporate it into a few of the scenes. It took a couple of tries to find the right placement and delivery, but lo and behold, the line was preserved in the final cut.

  • 3

    Taxi Driver — “You Talkin’ to Me?”

    A phrase that has been adopted by New Yorkers (or rather, those who impersonate them), “You talking to me?” was originally uttered by Robert DeNiro in Martin Scorsese’s Taxi Driver. In the script, the description for the scene simply read: “Travis talks to himself in the mirror.” Scorsese gave DeNiro free reign with his performance, making the actor perform long takes of improvisation until he began to unravel. Eventually, he got in the groove, delivering the iconic line to his crazed reflection. The rest is history.

  • 4

    Star Wars: Empire Strikes Back — “I Love You.” “I Know.”

    We can thank Harrison Ford for coining one of the most memorable Star Wars quotes to come out of the franchise. As Han Solo (Ford) is about to be frozen in carbonite, Princess Leia (Carrie Fisher) drops the L-word she had been holding back for so long. “I love you,” she tenderly tells him. Originally, Solo was supposed to reply with “I love you, too.” But he felt like that wasn’t in his character. So instead, he changed the line to “I know.” Not only does it add a layer of humor to the tense scene, but it speaks volumes about Han’s own nature and his relationship with Leia. It transformed the scene into something Star Wars fans still quote to this day.

  • 5

    Caddyshack — “Cinderella Story” Monologue

    Caddyshack director Harold Ramis knew about Bill Murray’s status as a master improviser, which is why he asked him to make up a speech in the style of a sports commentator. Murray delivered the story in character as groundskeeper Carl Spackler, coming up with the entire thing on the spot. The spur-of-the-moment monologue tells the tale of an unknown golfer winning The Masters, meandering for a good minute and a half as Murray whacks a manicured row of flowers with a golf club. It’s comedic gold.

  • 6

    Casablanca — “Here’s Looking At You, Kid”

    One of the most quoted lines in cinematic history, it’s hard to believe that “Here’s looking at you, kid,” wasn’t originally written into the script. Based on Murray Burnett and Joan Allison's unproduced play Everybody Goes to Rick's, the Casablanca screenplay was still in the works as filming commenced. Humphrey Bogart’s farewell to Ingrid Bergman was a popular phrase in the 1930s, and Bogart allegedly used it on Bergman off-camera while he was teaching her to play poker. The line stuck, perfectly matching the tone of the film’s melancholic ending. Bogart’s famous final line, "I think this is the beginning of a beautiful friendship," was dubbed in later, however.

  • 7

    Good Will Hunting — “He Stole My Line”

    Robin Williams’ performance as Dr. Sean Maguire in Good Will Hunting was so affecting, it won him his first and only Academy Award. Williams brought a touch of his signature magic to the role, which included some light improvisation. During one of his sessions with Will (Matt Damon), he fabricated the story about his wife’s flatulence mid-scene. Damon’s hilarious reaction in that moment is one hundred-percent genuine. But Williams’ best improvised line comes at the end, when he reads the letter Will left him before leaving for California. Williams came up with a new line for each take, but it was the humorously heartfelt “Son of a b—. He stole my line” that made the cut.

  • 8

    Frozen — “Oh, Look At That… I’ve Been Impaled”

    This is a case where a voice actor’s improvised line actually inspired the filmmakers to animate it. In Frozen, Josh Gad voices the naive, outgoing snowman Olaf. He delivers sunny one-liners and offbeat observations, including a moment where he notices an icicle has pierced his midsection. “Oh, look at that… I’ve been impaled,” he casually remarks. It’s a line that skews darker than the rest of Frozen’s family-friendly jokes, one that is very welcome in a movie that prides itself on being sweet and charming.

  • 9

    Titanic — “I’m King of the World!”

    Most cruise ships nowadays have to block off the bow of the ship to keep excited guests from flinging their arms to either side and screaming, “I’m king of the world!” The famous exclamation was made by Leonardo DiCaprio in James Cameron’s romantic epic Titanic, but it wasn’t always going to happen. Rather, Cameron told the 22-year-old DiCaprio to say the line on the spot, standing on the bow of the (prop) Titanic. Reportedly, DiCaprio had ad-libbed the line earlier that day, and Cameron felt it could be useful. DiCaprio’s unbridled enthusiasm was infectious — Cameron loved it so much he made sure the moment made it into the final film.

  • 10

    Willy Wonka and the Chocolate Factory — Willy Wonka’s Entrance

    Gene Wilder’s eccentric and brilliant portrayal of Willy Wonka is one of the great on-screen performances of the 20th century. Part of that is thanks to Wilder’s own imagination, which he brought to the script. When he emerges from his factory to greet his juvenile contest winners, he feigns a limp. Wilder specifically asked to add something special to his entrance, which would be a surprise to the child actors. When he did an unprompted somersault, their reactions were completely natural. Wilder also improvised Wonka’s unnerving chant delivered in the hellish tunnel during the children’s trippy boat ride down a chocolate river. The movie wouldn’t be as good with anyone else in the role.

  • 11

    Dazed and Confused — “Alright, Alright, Alright”

    At the time of filming for Dazed and Confused Matthew McConaughey was an unknown bartender living in Austin, Texas. He was originally cast as Wooderson, a three-day role in Richard Linklater’s Dazed and Confused, just enough to make some extra cash. But the brief stint on set turned into a longer one as Linklater asked McConaughey to improvise more scenes. This resulted in his character becoming much more prominent in the film, and it’s Wooderson who drives Pink and Mitch to the Emporium. It’s during this scene that McConaughey delivers his now iconic improvised line, “Alright, alright, alright.” McConaughey would then go on to improvise another memorable moment in The Wolf of Wall Street, where he used an acting warm up as an ominous chant in a scene with Leonardo DiCaprio.

  • 12

    The Shining — “Here’s Johnny!”

    Stanley Kubrick’s The Shining is bone-chilling for several reasons, but it’s mainly due to Jack Nicholson’s unsettling performance as the deranged Jack Torrance. As Jack becomes increasingly psychotic, he pursues his wife Wendy (Shelley Duvall) and son Danny (Danny Lloyd) throughout the Overlook Hotel. As Wendy pushes Danny out the bathroom window to safety, she remains stuck inside. Jack catches up to her, breaking through the locked door with an axe. He sticks his head through the door and sneers the words, “Here’s Johnny!” Nicholson’s improvised line comes from Ed McMahon’s popular catchphrase when introducing the harmless Johnny Carson on The Johnny Carson Show. What inspired Nicholson to add the line there is a mystery. But the way he turns the non-threatening, nostalgic line into a weapon makes the scene all the more terrifying.

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