McGee was originally stationed at the Norfolk Naval Base, making his debut appearance in the NCIS Season 1 episode, "Sub Rosa". He regularly aided the team with various problems and at the end of the Season 2 debut episode, "See No Evil", he officially joined Gibbs's team on a permanent basis and became known as the Probie of the team, something he maintained up until Season 7 when fellow colleague and former Mossad Officer Ziva David finally achieved her dream of becoming an NCIS Special Agent and thus, she became the "Probie" of the team.
In "Legend Part 1", much to the dismay of Anthony DiNozzo, the Senior Special Agent on Gibbs's team, McGee was chosen to accompany Gibbs to the Office of Special Projects in order to help them solve a case.
He also had regular contact with DiNozzo, voicing his suspicions in regards to Mossad spy Michael Rivkin.
Despite not appearing in NCIS: Los Angeles, McGee was mentioned in a discussion between Eric and Abigail Sciuto in the episode, "Random on Purpose" and again in the same episode when Abby, having been rescued after she was kidnapped and held prisoner by serial killer Tom Smith aka the Phantom had Eric get her a conference call straight to MTAC in the Navy Yard when she assured both Gibbs and McGee that she was fine.
- Sean Murray appeared in JAG as Danny Walden, the Admiral's stepson before landing a role on NCIS. Interestingly, the creator of NCIS and JAG, Donald P. Bellisaro is Murray's stepfather and his NCIS character is the son of an Admiral.
- Murray also holds dual-citizenship in both the United States and Australia.