After “Dark Angel” was canceled, Weatherly didn’t have to wait long for a meaty role to come to her. In 2003, he made his debut as Senior Agent Anthony “Tony” DiNozzo in Season 8 of the military courtroom drama. “JAG.” Weatherly co-starred with future co-stars Mark Harmon and Pauley Perrette in the episodes “Ice Queen” and “Meltdown”, which was intended to be the backdoor pilot for “NCIS”.
A few months after the “JAG” episodes aired, the “NCIS” pilot aired on CBS, kicking off Weatherly’s long stint as Tony DiNozzo. Tony becomes intimately attached to his wisecracks, often lightening the mood while he and his team solve gruesome cases. It’s almost unthinkable that DiNozzo isn’t joking or making any mention of the movie, but he could be a much sharper character without being affected by Weatherly.
Weather portrayed Tony until he bid farewell to “NCIS” at the end of its 13th season. In “Family First”, DiNozzo leaves Major Case Response Team so he can spend his time as a new dad, as the episode title suggests. After operating on “NCIS” for more than a decade, Weatherly is “ready for a new challenge,” according to The Hollywood Reporter.
https://www.looper.com/728251/the-transformation-of-michael-weatherly-from-childhood-to-ncis/ Michael’s Transition by Weather from Childhood to NCIS