In March 1941, Harmon signed a contract with Columbia Pictures to star in a motion picture titled, Harmon of Michigan, with filming set to commence in July 1941, after Harmon graduated from Michigan. The film was released later that year. His film appearances included two Paramount Martin and Lewis comedies as a sports announcer, That's My Boy (1951) and The Caddy (1953).
On October 10, 1941, the New York Americans of the rival American Football League announced that they had signed Harmon to play in the final four games of the 1941 season for around $1,500 per game.
In May 1941, the draft board in Lake County, Indiana, announced that Harmon had been classified as 1-B and deferred as a student until July 1, 1941. In July 1941, Harmon was granted a further 60-day deferment based on his claim that he was the sole support for his parents. In September 1941, he appeared in front of the draft board seeking a permanent deferment. His request was denied, and he was classified as 1-A. Harmon, then working as a radio announcer in Detroit, stated that he intended to appeal the ruling. His appeal was denied in October 1941, and he was given until November 1941 to enlist.