is the Lead Senior Special Agent and undercover operative attached to the NCIS Office of Special Projects. He speaks several languages fluently, including Russian. Callen is a highly skilled field agent having worked numerous overseas undercover assignments. Placed in the foster system at a young age, G. does not know his first name but is determined to find out about his family, and in turn, himself. As G. lives somewhat of a nomadic nature, Los Angeles is G's most stable home. He is partnered with Sam Hanna.