The popular character "Callen" (Chris O'Donnell) has been an integral part of the NCIS: L.A. team, which is supervised by "Hetty" (Linda Hunt), ever since day one. But how did "Grisha 'G' Callen" (who was born "Grisha Aleksandrovich Nikolaev") even get his job? It turns out that NCIS special agent in charge also started out small...

NCIS: L.A.: "Callens" difficult childhood

As a teenager, NCIS: L.A.'s "Callen" did not have it easy: His mother "Clara Callen" was half-Romanian and died when he was very young. She was murdered in the family feud with the "Comescu" clan. After that, the special agent went through 37 foster homes in the United States.

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Time and again, "Callen" got into trouble as a teenager. "Hetty" took the boy in and trained him. Before he became part of the NCIS L.A. team, however, he worked for the CIA, the DEA and the FBI, among others.

NCIS: L.A. "Callen" was part of the CIA

Several episodes of the crime procedural have given audiences an insight into his time at the CIA. In seasons one and two, NCIS: L.A. revealed that "Callen" worked at the CIA alongside the recurring character "Trent Kort" (David Dayan Fisher) and "Tracy Rosetti" (Marisol Nichols).

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In the past, "Callen's" grandfather, "George Callen", had also worked for the OSS (Office of Strategic Services, now CIA) and was stationed in Romania. "Callen" actually learned from "Hetty" in season three that his mother was also a CIA agent.

Chris O'Donnell has been playing "Callen" since 2009.

We learned in the very first season of NCIS: L.A. that "Callen" is also once worked with the DEA on behalf of the CIA and later with the FBI. Those days may be over, but "Callen" soon realizes that his past still affects his life today.

"Callen" also appeared in the the sixth season of NCIS. where he almost died in a drive-by shooting. The agent and team later found out that the shooting was related to a mission in which "Callen" had been part of ten years earlier as a DEA agent against the Russian mob.