Dissatisfied with the level of comfort, he starts designing and building improvements. After a while, Hell has air conditioning, flush toilets and escalators. The engineer is a pretty popular guy.
One day God calls and asks Satan, "So, how's it going down there?"
Satan says, "Hey things are going great. We've got air conditioning and flush toilets and escalators, and there's no telling what this engineer is going to come up with next."
God is horrified. "What? You've got an engineer? That's a mistake – he should never have gone down there! You know all engineers go to Heaven.
Send him up here! "
Satan says, "No way. I like having an engineer on the staff. I'm keeping him."
God says, "Send him back up here or I'll sue."
"Yeah, right," Satan roars with laughter, "and where do you think you are going to get a lawyer?"