Mark Harmon, who played Leroy Jethro Gibbs on the CBS series "NCIS," is reportedly undecided about returning for Season 21. Although he expressed interest in coming back, the launch of his book has occupied much of his attention. Some cast members, like Wilmer Valderrama, are not eager for Gibbs to return, as they feel it's their time to shine. Some fans believe Gibbs should stay gone, citing closure for his character and the show's need to move on. However, there are others who would like to see Harmon return in a limited capacity or for a proper ending.