13, 1972. Mark is the junior college transfer who ran for one touchdown and passed for another against the Cornhuskers. Mark Harmon had a bright future on the football field, but after his time at UCLA, he turned down offers to go pro in favor of an acting career. In this photo, Harmon is pictured in 1973.

In June 2019, Perrette tweeted she was "terrified" of Harmon "attacking" her. She said she was not returning to NCIS ever. According Vanity Fair, things soured between the two after Harmon's dog allegedly bit a crew member. "I can't speak to what she's addressing in her tweets.

In a special featurette for the NCIS Season 19 DVD, Harmon — who was also an executive producer on NCIS — hinted that he left the series “to keep it fresh in his career. “What has always drawn me here is the character I play and to keep it fresh and to keep it challenging,” he said.

Harmon was the brother-in-law of Ricky Nelson and John DeLorean and is the uncle of actress Tracy Nelson and singers Matthew and Gunnar Nelson of the rock duo Nelson. In 1987, Harmon filed for custody of his nephew Sam, Kristin's son, on the grounds that she was incapable of good parenting.