Today, each film's script is the hard work of a team of scriptwriters who toil over months figuring out what each character in the story will say and do to take the plot of the film forward. In fact, good scripts give each character distinct personalities that evolve as the story progresses.
However, sometimes, as directors start filming, actors might say or do something which might be scripted or an improvised version of the script, that might suit the story better than what was originally planned. These improvisations sometimes lead to rather iconic scenes.
Here is a list of films that have had improvised scenes added to them:1. Fast and Furious 6
In the film Fast & Furious 6, The Rock ad-libbed an insult making Ludacris spit out his drink as he couldn't stop himself from laughing too hard. The director decided to keep the scene for the ending of the film.2. Harry Potter and the Chamber of Secrets
Tom Felton who played Draco Malfoy in the Harry Potter and the Chamber of Secrets forgot his line while shooting and improvised on the spot which proved to be a funny scene. Take a look here:3. The Usual Suspects
For the film The Usual Suspects, the lineup scene was scripted to be done straight-faced, but actor Benicio Del Toro kept farting throughout the scene and no one could get through the scene without laughing. It turned out to be a great improvisation.4. The 40-Year-Old Virgin
In the film The 40-Year-Old Virgin, Steve Carell's chest was waxed for the very first time just like his character in the film. He assumed that it was not going to hurt so much and so when the wax stripped was pulled, it was a genuinely stunned reaction on Carell's face.5. Django Unchained
Leonardo Di Caprio, in the film Django Unchained, cut his hand by mistake while filming the iconic scene in the film. He decided to continue the scene anyway while spilling the blood all over the table and smearing it on Kerry Washington's face.
Well, talk about perfect timing and sheer luck to pull off such brilliant scenes and make them iconic through improvisations.