Seth Rogen was out of Knocked Up.
Knocked Up is a 2007 American romantic comedy film written , directed , and co-produced by Judd Apatow , and starring Seth Rogen , Katherine Heigl , Paul Rudd , and Leslie Mann . Seth Rogen . After Rogen received critical praise for his performance , Universal Pictures agreed to cast him as the lead in Apatow 's films Knocked Up and Funny People .