Paul The Alien Wasn’t Even On Set
While most alien movies are serious, Paul takes a hilarious turn–especially with Seth Rogen as the alien. Throughout his role, Rogen was also under contract for The Green Hornet, so he had to play Paul while not being on set.
A co-star, Joe Lo Truglio, acted in Rogen’s place during the shooting. Afterward, Rogen created some of Truglio’s lines and improv. He performed all the motion capture and voice acting post-production. In an interview with Collider, co-star Nick Frost admitted that he kept forgetting that Rogen was playing Paul.