Mark was a huge football star at UCLA where he was starting QB for two years and he stunned the football world when he didn't turn pro and went into acting. He has since 1987 been married to Pam Dawber of Mork and Mindy fame. Mark's acting goes all the way back to Adam-12 days in the 70s. He made a great movie with mega star Sean Connery and a lesser known at the time Meg Ryan. The movie was Persidio, in which Mark played a detective. Now at 57 Mark is the star of NCIS where he fits very well.
The only question left now is how is Gibbs going to get that boat out of the basement?