In the 2007 Judd Apatow comedy, Mann played Katherine Heigl's sister, Debbie, who's married to Rudd's character, Pete, a talent scout with a penchant for fantasy football and solo movie outings. Seth Rogen also starred as Heigl's baby daddy.
Apatow, Mann's real-life husband, will write and direct the as-yet-untitled film. It is unknown if Heigl or Rogen will return.
Knocked Up earned more than $200 million worldwide. The sequel is set for release in 2012.