Mark was tapped to replace Don Johnson on Miami Vice during the show's third season when Johnson was being difficult about his contract. But when Johnson finally agreed, Mark never even appeared on the show.
Mark studied sign language for his various television roles with The Sign Language Company, run by actor Bill Pugin.
Mark worked as a tennis-shoe salesmen prior to getting his big break in acting. His salesman days have obviously not been forgotten as he now owns over 100 pairs of sneakers.
Mark received the nickname 'Quarterback' because his dad was an announcer for the football games that Mark played in when he was younger. His dad did not want to call Mark by name, so instead he called him Quarterback.
Mark has broken his shoulder twice - once during the filming of the movie Summer School.
The hand tools that Mark Harmon uses on the set of NCIS, are mostly his own. Those are the tools that he uses in his own personal workshop.
Mark took part in a celebrity baseball match in 2006 which raised $243,785. The proceeds from the even went towards The Children's Center.
Mark has an abducted left knee from his football career.
Mark has appeared naked in two movies during his career; Sweet Bird of Youth and Basic Deception.
Mark has appeared in over 20 Coors Beer commercials.
Mark played Robin Prince in 1986's made for TV movie, Prince of Bel Air alongside Kirstie Alley.
Mark Harmon enjoys holidaying in Montana on a Cattle Station, while riding horses, and doing all those cattle station kinds of things. He has been going up there since 2001, taking his two children and lovely wife, Pam.
Mark enjoys road trips, especially following unknown roads to places that he's never been before.
Mark Harmon has been known to wear shirts which have been sent to him by his fans.
Between 1977 and 2002 Mark was nominated for four Golden Globe awards and two Emmy Awards.
Mark is a big baseball fan and used to be part-owner of the San Bernardino Spirit minor league team.
On the set of NCIS, Mark uses a 1972 Airstream trailer that he restored himself as a "Dressing Room". The trailer has avocado green benchtops.
Mark is Roman Catholic.
Mark dated actress Heather Locklear in the early part of the 80s.
Mark worked as a carpenter before he hit it big.
Mark has 2 sisters in the entertainment business. They are Kelly Harmon and Kristin Harmon.
Mark was the brother-in-law of singer/actor Ricky Nelson, as his sister was married to Ricky from 1963-1981. The marriage also means that Matthew and Gunnar Nelson (aka Nelson, the band) are his nephews, and actress Tracy Nelson is his niece.
One of the most notorious characters that Mark played was serial killer Ted Bundy 1986's TV movie, The Deliberate Stranger.
Mark graduated cum laude from UCLA with degree in communications in 1974. He also played quarterback position for UCLA Bruins, 1972-73, winning National Football Foundation Award for all-round excellence.
In 1986 Mark was chosen as People Magazine's Sexiest Man Alive.
Mark risked his life to save two teenage boys who were involved in a car accident outside of his home. Harmon used a sledge hammer from his garage to break the window out of their car then pulled them free before they burned to death while his wife Pam Dawber called 911. He made every effort to downplay his role in saving their lives.
Mark and Pam Dawber have two children: Sean Thomas Harmon born 26 April 1988 and Ty Christian Harmon born 25 June 1992.
Mark Harmon: (On job security) I've never done any job for the security or the money. I believe in trying to find an area to get better, to learn more about why I'm here.
Mark Harmon: (when asked about how he copes with the medical jargon on Chicago Hope) Yeah, absolutely. It's like a different language, but at Chicago Hope they have a technical staff that works real hard to make that comfortable. They will work as hard on the stuff we do in the O.R. or on the operating field as anything. There are actually rehearsals separated from the rest of the show to perform that and try and make that as realistic as possible.
Mark Harmon: (On carpentry) I used to hang out in my Dad's workshop on weekends. Later, when I was starting out as an actor, I became a roofer and a framer to make money. But what I really enjoyed was the finished work. I like the longevity.
Mark Harmon: (on knowing he wanted to act since he was six years old) I subconsciously began to realize that I wanted to entertain people.
Mark Harmon: I have to be challenged. The busier I am, the better I like it.
Mark Harmon: (On how he gained stardom) A lot of times, discipline and hard work can make up for the talent you don't have.
Mark Harmon: If other people think I'm okay looking, that's great, but I don't see it myself. When I look in the mirror all I see is a bunch of fake teeth and football scars.
Mark Harmon: Women would come up to me and show me their breasts and ask for my opinion, and I gave it to them.
Mark Harmon: That's what excites me about being an actor, the idea that I can get up every morning and try something new and grow and change. I'm not worried about image. I wouldn't have done the AIDS storyline if I weren't. I'm an actor.
Mark Harmon: I don't get lulled into comfort, I like walking on the edge.
Mark Harmon: I was pretty average stuff as an athlete. I wasn't fast, I made up for it by working harder.
Mark Harmon: I was raised with the idea of maximum effort, as long as you could look in the mirror and say 'I gave it everything I had' it was OK. But if you gave it less, that would disgrace you.
Mark Harmon: (On his NCIS character & the show) Jethro doesn't think of himself as a hero, which is maybe what I like best about him. He's an old-school leader. People perceived this show to be one thing but it has proven to be something else. To me, what made the show different was how these characters were not predictable and there was humor.
Mark Harmon: (On his Chicago Hope character) John Tinker initially told me that he wasn't sure what kind of surgeon I'd be, but he knew I'd wear clogs and be complicated. I said, 'Great!'
Mark Harmon: (On his St. Elsewhere character) The character changed dramatically in the third season. He went from caring surgeon to womanizing sleazeball. Originally, I was going to get Lou Gehrig's disease. But Paltrow changed it to AIDS. Bill Daniels' character said to Bobby, 'I didn't even know you preferred guys.' And I said, 'I don't.' That was an important piece of information to get out because there was a consensus at the time that AIDS was the result of a certain life and that was dead wrong.
Mark Harmon: She's a great mum, a great lady, and I truly admire her and I'm fortunate.
Mark Harmon: I'm a Michael Caine fan. He was so nice to me and he didn't have a reason to be.
Mark Harmon: We have a book that we just write down what the kids say. You forget...and when you read the book you remember and it's amazing.
Mark Harmon: Gibbs is like a great hunting dog – he is just the guy you want in your fox hole, he is just the guy you want to ride the river with, I don't know if he's the guy you want to have dinner with.
Mark Harmon: (Speaking about 'And Never Let Her Go') As an actor, I look to play roles that challenge me and this did that. I asked to speak to [the victim's sister] Kathleen Fahey and did. My pledge to her and to her family was to make every effort to play this guy honestly. I don't take that responsibility lightly.
Mark Harmon: (On acting) The only other job I've ever had that provides that time in the morning where you're going to work and you can't wait to get there and the sun's rising and you're moving toward something you look forward to getting up and doing every day was being a carpenter. And it was because you're doing something different every day.
Mark Harmon: It's a lot easier to do good work when you have good words to say and work with good people.