Knocked Up
Jay Baruchel, who also played Jay in Knocked Up, was genuinely afraid of roller coasters. However in the DVD commentary, we learn that the crew manipulated him into riding a roller coaster for the opening credits. Why? They knew it would for great viewing.
Bridget Jones’s Diary
The fight scene that took place between Mark Darcy (Colin Firth) and Daniel Cleaver (Hugh Grant) was totally original. As in, it wasn’t choreographed! The actors just made it up as they went along and well, it was hilarious.