不完全体セル was Cell’s first [imperfect] form prior to his absorption of the Androids. Cell hailed from the future where neither 17 nor 18 were present, having already been taken out by Trunks. In order to complete his evolution, Cell stole the boy’s time machine to go back in time but in order to fit into it, Cell had to revert to an egg. He hid underground for four years until he grew back to his humanoid self. After emerging, Cell feared he didn’t have the power he needed to forcibly absorb the Androids. To increase his strength, his first actions were to exterminate several towns, absorbing the inhabitants within.
Cell, by Raph.