Seth Rogen has lifted the lid on what happened behind the scenes on Knocked Up, revealing why an A-list actor who had been due to star opposite him quit the project.
The hit 2007 comedy, written and directed by Judd Apatow, saw Katherine Heigl play high-flying TV producer Alison, who found out she was pregnant after a one-night stand with Ben Stone, an unemployed (and appropriately named) stoner played by Rogen.
