John Christopher Reilly (born May 24, 1965) is an American actor, singer and comedian best known for his roles as Happy Jack Mulraney in the 2002 historical film Gangs of New York, Amos Hart in the 2002 musical film Chicago, Dan Brown in the 2002 drama film The Hours, Dewford Randolph "Dewey" Cox in the 2007 music comedy film Walk Hard: The Dewey Cox Story and as Dale Doback in the 2008 buddy slapstick comedy film Step Brothers (co-starring Will Ferrell). He hosted Saturday Night Live on October 21, 2006.