The casting director told Natalie Portman she was too young. She was 11 years old, had never been in a film, and went around him to ask the director for a second audition. Out of 2,000 girls who auditioned, she got the role.
Léon cost $16 million and grossed $45 million worldwide. France alone sold 3.6 million tickets, with the film at number one for three straight weeks. The film almost didn't exist, and nearly everything people remember about it happened by accident.
Luc Besson got the idea while making La Femme Nikita in 1990. Jean Reno played a minor character called "Victor the Cleaner," a hitman who shows up for two minutes, removes a body, and leaves. Besson thought that character deserved his own film. He called the early draft "The Cleaner." Mel Gibson, Robert De Niro, and Keanu Reeves were all offered the lead before Besson went with Reno.
The film got made because Bruce Willis delayed a different production. Besson was already planning The Fifth Element, a sci-fi film, when Willis's schedule pushed the shoot back. He used that window to make Léon.
Gary Oldman improvised many of his key scenes. The Beethoven monologue, where his character talks about classical music while threatening a drug dealer, was unscripted. Oldman filmed it several times, giving a different speech on each take. The scene where he sniffs a suspect: also improvised.
Near the end of the film, Oldman's character has to order every available officer to storm a building. The take that made the final cut started as a joke. Oldman told the soundman to take his headphones off, then screamed the line at full volume. Besson loved it and kept it. One publication later called Oldman's character "the role that launched a thousand villains."
Portman said she didn't have to act at all in her scene with Oldman. She was scared. It showed.
During a location shoot in New York, a man who had just robbed a nearby store sprinted onto the set, saw a block full of police cars, and gave himself up. Every officer on that block was an extra in costume.
Americans who saw this in 1994 watched a version 23 minutes shorter than the rest of the world. Those scenes were cut after test screenings in Los Angeles went badly. Besson has said the longer version is the film he always intended to make. It has been on DVD since 2000. If you've only seen the American cut, there's a different film you haven't watched.