[5] While studying at the Professional Children's School[2] in New York, he was cast as Tommy Gordon in the 1935 Broadway production of Sidney Kingsley's Dead End[6] and traveled to Hollywood with the rest of the Dead End Kids when Samuel Goldwyn produced a film version of the play in 1937.

He played the bully Harry Flashman, speaking with an English accent, in the 1940 film Tom Brown's School Days opposite Cedric Hardwicke and Freddie Bartholomew.

After serving in World War II in the US Army Signal Corps, he found that he had grown too old to be effective in the roles that had brought him fame.

Diminishing film work, marital difficulties, and a drinking problem eventually ate away at his show business career.

[citation needed] In the 1970s, Halop enjoyed a career resurgence playing the character Bert Munson, cab driver and close friend to Archie Bunker on the television series All in the Family.