

The most recognizable feature of Jack robots, however, is the distinctive head and face, complete with trademark Mohawk hairstyle, shared by all models of Jack robots. This is especially apparent in the Jack-7 model, where a green glow radiates from the joins in his skin. While earlier models looked relatively human, the later models have sectionalized skin, making them appear less human. The Jack robots, throughout their many incarnations, have maintained the same general appearance - humanoid juggernauts with bulging muscles. Jack-6's personality is explored a little more when playing as him in the Scenario Campaign in Tekken 6, where he is vocal of his love of fighting, strong opponents and fellow robots, and, while he is programmed to understand longer words like "biologicals" (his name for humans), he generally has a very child-like way of thinking and speaking, failing to understand a lot of what the other fighters are saying to him, and labeling anything unknown or unfamiliar as "bad". However, Jack robots are also able to show empathy and compassion, as demonstrated by Jack-2's reaction to finding Jane, and seem to be very protective of those with whom they share a close bond, even going so far as to sacrifice themselves, as demonstrated by Gun Jack in his Tekken 3 storyline. Having been built as a destructive killing machine, Jack robots are very aggressive, and do not hesitate in destroying all in sight. Starting with Jack-2, Jane transfers the memories and sentience of the latest playable Jack to the next playable model, meaning that all the playable Jacks after that have technically been the same "Jack". After this, Jane joined the G Corporation, where she continued to work on building Jack robots in the hope of restoring her beloved companion. Although Jane was successful in installing Jack-2's memories into the new Gun Jack model, Gun Jack was ultimately destroyed.

After this, Jane, the young girl rescued by Jack-2, grew up determined to restore the robot who saved her as a child. Suddenly developing a conscience, Jack-2 took it upon himself to look after the girl, up until the point he was destroyed by Doctor Abel. During this time, one of the Jack-2 robots came across a young girl. After proving himself in the first King of Iron Fist Tournament, updated Jack robots were put into mass production and utilized in battlegrounds. It was a killing machine built purely for destruction. The first Jack was built by the Russian military, though with programming data provided by the Mishima Zaibatsu.
