The past, present and future walk into a bar. It was tense.
In Good Spirits:
A man entered a bar and asked for a bottle of beer.
Soon he brings it back unopened and asks for a shot of liqueur instead. He drinks it and begins to leave without paying. The bartender stops him. "Hey, you haven't paid for the drink."
"But I gave you the beer in exchange."
"You didn't pay for that either."
"But I hadn't opened it."