Mr. Z is a mysterious and unseen character in the Gman Squad series of machinimas and improvised skits. Although he has appeared only once, his message weaves a storyline that lasts for three episodes. He is also the last of the three mysterious identities in the series, and the one who created the trap for the Gman Squad in the episode Grunts to prevent them from making any mischief again, like the event that happened at Black Mesa.
More of his identity is explored and explained in-depth in the beginning of Trams.
In the Brothers of the G-man squad, Mr. Z was the one who sent the Matrix G-man (real name Gmanator) to kill the G-man squad.