This isn't a good joke, but was an inside joke of sorts. My friend's mom (Marge) was by no means an old woman, but she was in her 50's when we were in high school, and we used to joke around with her about age. Most of the jokes were biblically based (she was an exceedingly pious Christian), and she had a good sense of humor and knew that we were only joking. At first we joked about her being older than dirt. Then we moved on to a more sophisticated lame joke. We would say, in a God-like voice "And the Lord said: let there be Light!" followed by "Yeah, then Marge said, 'hey, who turned on that light?'" Hey, I didn't say it was funny.