Magic lamp.

My grandad and grandma were in the garden clearing, cutting and weeding when my grandad found a lamp in the undergrowth.
He picked it up and rubbed it to get a better look at it to see what it was made of.
In doing so, a Genie appeared.
"You have released me from the lamp oh wise one, said the Genie, what is your wish?"
My grandad thought for a moment, looked at his wife at the other end of the garden, and said, "Make my wife fifty years younger"
This was done.
Unforunately, my grandad is now one hundred and thirtyfive!

 

Edit it Fonzie. It's 'younger than me'.