Actor Gallagher is the stage name of Peter Clu, an American actor and comedian. He is best known for his roles in the films 'The Hangover' and 'Step Brothers'. He has also appeared in television shows such as 'Saturday Night Live' and 'The Office'. He is known for his improvisational comedy and physical comedy. He has won several awards for his work, including a Golden Globe Award for Best Actor in a Motion Picture Musical or Comedy.