With out even a space suit to shield him to from the surrounding vacuum, he was sucked, along with the rest of flotsam, into a laboratory beneath the lunar crater Ptolemy. Fearful of being perceived as enemies of Earth, the aliens running the place, Si-Krell and Plentha, repaired his smashed body with parts they had around, making him (with the inexplicable exceptions of his head and hands) look like a human-shaped pile of jigsaw puzzle parts, hence the name . In his souped-up body he is pliable and super strong so when he got back to Earth he went into the superhero business.
