In several episodes you get a rehashing of Dr. Farnsworth and Mom's relationship but it always seems to start in different ways. How many times did they actually date?
2927: Dr. Farnsworth designs the fuel-inefficient sport-utility robot, from which is derived all future robot designs, leading to global warming. In 2931 he breaks up with Mom again and leaves the company. (episode: "Crimes of the Hot")
3001: The two get back together briefly for some "hot, dry sex". (episode: "Mother's Day")