A university professor had a standing order at his preferred bar: a strawberry daiquiri stirred with a small stick of walnut wood, which was to be left in the drink when it was served. Every afternoon, the professor would come in at almost the same time (right after office hours), and the bartender would have the daiquiri waiting for him.
One day, the bartender realized he was out of walnut sticks. He went to his supplier - but the supplier was out too. "All I can give you in that size," the supplier said, "is hickory - is that going to work?"
"I guess I'll make it work," said the bartender, and returned with the hickory sticks. As the hour approached, he selected one, made the daiquiri, swirled the stick around it as usual, and set it out for the professor.
The professor, though, took one sip and said, "Hey, this isn't walnut, what gives?"
The bartender sighed. "You got me - they were out of walnut. It's a hickory daiquiri, Doc."
I was going to tell a joke about empty canopic jars, but my heart's not in it.
(This is also funnier if autocorrect doesn't mess up "canopic", dang it)