The prototype for Jack was developed in Russia. Since it was just a step in the production, the skin was removed from the mecha. Prototype Jack (or P. Jack, for short) was built only for power, so his power capacity far surpasses that of the completed Jack. The tournament's sponsor, Heihachi Mishima, has entered P. Jack into the contest in order to face him against Jack.
After the first Rave War, the remains of the first Prototype Jack unit (a first-stage model of the final Jack model) were almost destroyed by Jack's rampaging combat abilities. Upon reactivation, P. Jack complained that his alter-ego had received a refit, and he repeated his plea until his fuel ran out. Now resting in Kazuya Mishima's laboratory, P. Jack was left untouched for months before a back-up fuel supply reactivated him, and once again he began his constant pleas for a new look. To quiet him, Kazuya gave his captured scientist, Doctor Bosconovitch, the task of remodeling the robot.
With a cunning memory change, the doctor managed to convince P. Jack that his new body afforded him superior protection to Jack's, despite it being only a hat and sunglasses. Kazuya is currently goading P. Jack to demand more programmed maneuvers in time for The King of Iron Fist Tournament 2. Having repeated his fighting moves over and over (to such an extent that the doctor disconnected P. Jack's voice box), P. Jack now feels his next encounter with Jack will have a much different conclusion.
Ending Description: Prototype Jack is traversing inside a tunnel and turns his leg booster on in a vertical opening. He comes out of the shadows and flies straight up into the sky. As he flies away, he explodes and three screws have fallen out onto the ground.