How did McGee join NCIS? The Probie's full origin story
Timothy McGee has now outlasted every single member of the original NCIS cast — including Mark Harmon's Gibbs, who left in season 19. Which is funny, because McGee was never supposed to appear in more than one episode.
He exists because of a script problem the writers had three days to solve.
The accidental creation
The episode was "Sub Rosa," season 1, episode 7, aired November 18, 2003. The plot sent Gibbs and Kate onto a submarine to investigate a murder — which left Tony DiNozzo working the case alone on shore. Former showrunner Frank Cardea explained the problem on the Partners & Probies podcast in 2026:
"We can't have Michael talking to himself," Cardea said.
The fix: the writers discovered the term "probie" — a brand-new probationary agent — and invented one stationed at the NCIS field office in Norfolk who gets pulled into the case. Sean Murray was cast, McGee spent the episode nervously calling Tony "sir," and the chemistry was obvious enough that a one-off guest spot turned into a recurring role on the spot.
The Norfolk years
In-universe, McGee starts as a green case agent assigned to Norfolk Naval Base — an MIT and Johns Hopkins graduate whose computer skills keep making him useful to Gibbs's team. He appears in eight episodes across season 1, assisting whenever the case needs someone who can actually operate technology.
Joining the team for real
At the start of season 2, in September 2004, Gibbs brings McGee to the Washington Navy Yard as a full-time member of the Major Case Response Team, and Murray joins the opening credits. Some housekeeping on his slow climb from there:
- Probationary agent — his official status for roughly six years, and the source of DiNozzo's eternal "Probie" nickname.
- Senior Field Agent — the job he inherits when Tony leaves in season 13.
- Acting Director — he even runs the whole agency temporarily in season 20.
The family connection
One more piece of the origin story: Sean Murray is the stepson of Donald P. Bellisario, who created both NCIS and its parent show JAG — where Murray had already played the admiral's stepson, Danny Walden. Bellisario personally asked Murray if he wanted the one-time rookie part, per Murray's 2024 TV Insider interview. Nepotism rarely delivers a 20-plus-year return on a single episode, but here we are.
For the record: McGee also secretly wrote bestselling crime novels on the show under the pen name "Thom E. Gemcity" — an anagram of Timothy McGee.
The books ' agent character, "Lisa," was an anagram too. Ziva was not amused.