Several years before making his debut on Ozzie's Girl, Mark, then barely a high school student, made his commercial debut for a Kellogg's ad, alongside his dad Tom Harmon. Tom, who passed away ...

Mark Harmon's son, Sean, portrayed a younger version of his father's "NCIS" character several times, so why didn't he reprise the role for "NCIS: Origins?" ...

Before his iconic role, Mark was on the verge to becoming a quarterback for the NFL. This comes as a surprise to some but little did many know, his father, Tom Harmon, was a Heisman Trophy winner ...