Jack was an Australian aboriginal whose mutant powers were telepathy and radar sense, which allowed him to scan his surrounding area. His powers had a side effect where his body became petrified and brittle every time he used them.
At his trailer in Australia, Jack was attacked by Sauron, who was an agent of the new Weapon X program. After their encounter, Sauron offered Jack the chance to join Weapon X. Thinking that Weapon X was a superhero team and they could fix his mutant side effect, Jack accepted. After getting some money at the Bank of Australia and saying good-bye to his girlfriend and dog, Jack left with Sauron to join Weapon X. Along the way Jack made a joke about Sauron and the Director. This enraged Sauron and he literally tore Jack apart. Though he was in pieces, Jack survived. Sauron put Jack in a box, and brought him to the Weapon X compound. There, Jack used his telepathy and discovered the Director's plans for him.
Jack was being utilized by the Weapon X program as a mind-reader during the admissions process for captured mutants incarcerated in the "Neverland" concentration camp. It's unknown if Jack-in-the-Box kept or lost his mutant powers after the M-Day.