An Irish man frees a genie and happy to be released from his confinement, the genie grants him 3 wishes.
The Irishman thinks about it, and says "I want me a pint of Guinness that is never empty."
So poof a pint appears, filled to the rim with the rich brown drink. The man drinks it down, and when he places it back on the bar, it's filled up again.
"So, what would you like for your other two wishes, sir?"
"I want two more of these, then!