G-Man (slang) the Movie of the same name. G-Man (slang) G-Man (short for "Government Man") is an American slang term for special agents of the United States Government. It is specifically used as a term for a Federal Bureau of Investigation (FBI) agent. "G-Man" is also a term used for members of G Division, essentially a British anti-rebel police unit operating out of Dublin Castle prior to Irish Independence in 1922. Colonel Ned Broy uses the term in his official testimony for the Irish Army's Bureau of Military History in their archive of the Easter Rising (1916) and the Irish War of
G. Callen G. Callen G. Callen (born: Grisha Alekandrovich Nikolaev) is a fictional character in the show "" portrayed by Chris O'Donnell. He is an NCIS Special Agent in Charge, and the senior agent assigned to the Office of Special Projects. O'Donnell made his first appearance during "NCIS" sixth season episode "Legend (Part 1)". Before working at NCIS, Callen previously worked for the CIA, DEA and FBI. Several episodes across the seasons reference his stint with the Agency and in seasons one and two, it is revealed that whilst with the CIA, Callen worked alongside recurring "NCIS" character, Trent Kort (David Dayan