List of NCIS: Los Angeles characters

Agent Grisha "G." Callen (born: Nikolaev) (portrayed by Chris O'Donnell) is the NCIS Special Agent in Charge, and the senior agent assigned to the Office of Special Projects. He first appeared in the ''NCIS'' season six episode "Legend (Part I)".

Before working at NCIS, Callen previously worked for the CIA (the longest), DEA, and FBI. Several episodes across the seasons reference his stint with the Agency. In seasons one and two, it is revealed that while with the CIA, Callen worked alongside recurring ''NCIS'' character Trent Kort (David Dayan Fisher), and was partnered with Tracy Rosetti (Marisol Nichols). Callen once served with his friend Leroy Jethro Gibbs, who now works at the NCIS Headquarters located in the Washington Navy Yard. Callen specializes in deep undercover work. Prior to the series commencing, G. Callen and Sam Hanna had been partnered for two years (as per the season three episode "Partner" where they celebrate their five-year partnership).

In the show's first episode "Identity", it is revealed that he is called "G" not because he dislikes his first name, but because he does not actually know what it stands for, as the system never told him. Further insights into his childhood come in season one's "Pushback", where Hetty Lange and operational psychologist Dr. Nate Getz discuss how Callen lived in thirty-seven foster homes from the age of five to the age of eighteen, sometimes moving every few days. Callen's childhood was fraught with abuse, which is referenced during various episodes. In season one ("Keeping It Real") he recalls that he once watched his foster father beat his foster brother to death. In season four, he shares how moving unexpectedly to a new home that wasn't quite so nice, made him close off his feelings. In "Reznikov, N." (season five), Callen tells Kensi and Deeks that when he was ten, his foster father used to beat him with a broom handle.

Over the course of several seasons, Callen has discovered more about his identity and flashbacks in the season two finale prompted him to suddenly recall that he spent part of his early childhood on the Romanian coast of the Black Sea. He also uncovers repressed memories of witnessing his mother being assassinated in front of him when he was four. Early in season three, Hetty finally tells Callen that she knew his mother, Clara and she was her CIA handler. Callen's maternal line back to his grandfather George Callen is revealed, as well as the Romanian blood feud between the Callens and the Comescus.

In addition to English, Callen is fluent in at least six other languages: Spanish, Polish, Russian, German (which is claimed to be Austrian, and is usually completely butchered), Italian (with a Northern accent), and French. Callen also claims to speak Czech and Romanian; furthermore, his Russian is arguably good enough to be taken for one, but not the other, Chechen dialect. In the Season 1 episode "Search and Destroy" (S1:E4), Callen is shown easily reading Arabic, with enough fluency to translate on the fly into idiomatic English. Provided by Wikipedia