J.A.C.K. is an automaton created in Colton Wynant's automaton's factory. It was brought to Mars by Wynant to measure who was the quickest draw in the quick-draw contest designed to find the new sheriff on Mars. Wynant, however, built in knowledge of the local laws and other information to also present it as a possible candidate for sheriff as well.
One of Wynant's employees, Thanxley, had also upgraded J.A.C.K. with sentience in an effort to convince Wynant to manufacture robots instead of just automatons. This caused J.A.C.K. to go rogue and attempt to kill the people present. J.A.C.K. was eventually shot and killed by Bill Clover.
- Sheriff on Mars (TAH #162)