Complex sentence: The idea for "Sleeping Giants" first came to him when his son asked him to build a toy robot, for which he wanted an extended back story about where the robot came from and what it did.
Split into simpler sentences: The idea for "Sleeping Giants" first came to him when his son asked him to build a toy robot. Not just any toy robot, he wanted one with an extended back story, wanted to know where the robot came from and what it did.