153 is stylized with long red "Weasel" hair and a red coat. In Thing-Thing 3, he wore plain black shoes, but in Thing-Thing 4, they are replaced with metal plated boots. He also had what appears to be eyeliner in Thing-Thing 4, as well.
While not as physically capable as 154, he is a clever strategist with complete awareness of his surroundings, an advantage to normal pilots. 153 is also capable of wielding firearms to an efficiency similar to 154's, even while operating a vehicle. Because of his nature as a pilot, 153 relies on indirect methods against any and all enemies. Outside of operating complex machinery with relative ease, he appeared to have some form of authority over Systems Corp.'s ground forces, having organized them in the pursuit of 154 at the company's corporate headquarters.
He first appears in Thing-Thing 3 as an anonymous lead until you meet him in the third level. Here, he battles Project 154 in a bipedal mobile armor while wielding a Benelli M4 shotgun. He flees upon defeat, but not before collapsing the floor underneath Project 154, leading him to the containment chamber. 153 had also dug out Vahl Dreig from the bio-waste disposal area and reactivates him, before pitting him against 154. After 154 defeats Vahl Dreig, 153 reminds him that he is still trapped in the containment chamber.
He reappears in Thing-Thing 4 where he confronts Project 154 at Systems Corp.'s corporate headquarters, with a Bren-10 in hand and a platoon of soldiers under his command. 154 flees by jumping out the window and hi-jacking a sports car, but 153 gives chase in an attack helicopter, intending to finish his feud with 154 once and for all. 154, unfazed, shoots down the helicopter with a Heckler & Koch HK21 found in the car, and Project 153 is presumed dead.