Special Agent G. Callen is an orphan who was raised in the state welfare system, in 37 foster homes. His legal name is G Callen; when asked what the letter 'G' stands for, he said that no one ever told him because his parents left him when he was a kid and all he has ever found out is that it started with 'G'. Callen learned to speak Russian at age fourteen from his foster sister Alina Rostov during the time Callen lived with her family as an adolescent
Special Agent Callen's career with NCIS has included assignments in Serbia and Russia. On two separate occasions Callen's life was saved by Leroy Jethro Gibbs, once in Serbia and once in Russia.
Currently, Callen is serving as a the supervisory agent for a team attached to the Office of Special Projects. As a member of OSP Callen's current partner is Special Agent Sam Hanna.
At the conclusion of episode 6.23, "Legend, Part Two" Special Agent Callen was wounded in a drive-by shooting witnessed by Special Agent Hanna. The motive for the shooting has not been disclosed, however the Russian woman next to his apartment is seen to have left immediately after his shooting, smiling.
In episode 6.24 entitled "Semper Fidelis" it is said that Callen also knows Tobias Fornell as he inquired after Callen, and Gibbs told him that Callen's condition was still critical. Ironically before being shot Callen had remarked to Hanna that he thought it was time for him to move again, and that he felt as though he was being watched. Four months later Callen returned to his duties.
The case was closed when it was revealed that a former CIA operative Ethan Stanhope arranged the assassination attempt. Stanhope desired to eliminate all persons with knowledge of Operation Cossack a joint NCIS-CIA operation in Russia that failed when it was compromised by Stanhope. Stanhope's goal was to conceal his treasonous actions and prevent any adverse disclosures that would have harmed his business ventures.
