343 Guilty Spark (often called Nanny) is a robot built by ancient people from A Long Time Ago in a Galaxy Far Far Away. He, became Master Chief's nanny when he found Halo. But he hated her, and blew her up after she tried to kill him.
343 Guilty Spark was very guilty, as she often killed anyone who went on a Halo. Master Chief was so awesome, she didn't kill him, and just nagged. She only attacked because he was trying to blow up Halo. She doesn't like him anymore, probably because he blew her up with a SPARTAN LASER!
343 go boom.