Gibbs!
Now, here’s a surprising choice for an actor to play Gibbs…Harrison Ford! At the time, Ford was experiencing a slump and was encouraged to audition for the role of Gibbs. However he decided not to pursue the role. In the first episode of NCIS, Harmon drops Ford’s name and the classic film Air Force One. A subtle nod, perhaps?
Santa Claus
Between seasons three and four, Mark Harmon received a call which informed him that he needed to immediately stop shaving. Why? Well, going forward, his character would need to sport a scruffier look, along with a mustache.