David Ian Hewlett ( born 18 April 1968 ) is an English-Canadian actor , writer , director , and voice actor best known for his role as Dr. Meredith Rodney McKay on the Canadian-American science fiction TV shows `` Stargate SG-1 '' , `` Stargate Atlantis '' and `` Stargate Universe '' .
David Ian Hewlett ( 18 April 1968 ) He is an English-Canadian actor , writer and director . He is best known for his role as Dr. Meredith Rodney McKay on the science fiction TV shows `` Stargate SG-1 '' , `` Stargate Atlantis '' and `` Stargate Universe '' .