The 71-year-old has appeared in a variety of major TV shows and films over the course of his career, including The West Wing and Freaky Friday. But did you know that he made his TV debut in the NBC sitcom Ozzie's Girls back in 1973?
The actor bagged a part playing Mark Johnson, a college friend of Susie's who runs against her for class president. At the end of the episode, it's revealed that Mark won the election and offers Susie a position as his advisor before celebrating on the dance floor. Watch him in action below!
WATCH: Mark Harmon shows off his dancing skills in Ozzie's Girls
Mark has his older sister Kristin to thank for his first screen credit as she was married to show creator Ozzie Nelson's son, Ricky.
Following his small screen debut, Mark went on to appear in minor roles on various TV shows before landing his big break playing Dr. Robert Caldwell in NBC's medical drama St. Elsewhere in 1983.
Mark has been on our screens since 1973
He stayed in the role for three seasons before making his departure in 1986, when his character contracted HIV - one of the first times a recurring television character was diagnosed with the virus.
From there, the actor landed several starring roles on primetime shows, including police drama Reasonable Doubts and the crime mini-series, The Deliberate Stranger, in which he portrayed serial killer Ted Bundy.
Mark - who married his wife Pam Dawber in 1987 - also made a name for himself on the big screen, co-starring alongside Sean Connery and Meg Ryan in the 1988 film The Presidio and also opposite Jodie Foster in Stealing Home.
Mark Harmon with Meg Ryan in the 1988 film The Presidio
Following his four-episode story arc on The West Wing - which won him his second Emmy nomination - JAG and NCIS creator Donald P. Bellisario invited him to guest star as Agent Gibbs in two episodes of JAG in 2003.
Just a few months later, Mark starred as the same character in the show's spin-off series, NCIS - a role that he played for almost two decades until 2021.
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