Grisha "G." Callen is a fictional character in the show NCIS: Los Angeles portrayed by Chris O'Donnell. He is an NCIS Special Agent in Charge, and the senior agent assigned to the Office of Special Projects. From Wikipedia
In Season 22, Episode 18, Hanna leaves lobbying to rejoin fieldwork, delivers updates on Callen, Anna, and Tennant, and hints at Hetty Lange's location in a DMZ.
