"Surely You're Joking, Mr. Feynman!" - unam.

same waitress all the time.
I noticed that they were always in a hurry, rushing around, so one day, just for
fun, I left my tip, which was usually ten cents (normal for those days), in two nickels,
under two glasses: I filled each glass to the very top, dropped a nickel in, and with a card
over it, turned it over so it was upside down on the table. Then I slipped out the card (no
water leaks out because no air can come in ­­ the rim is too close to the table for that).
I put the tip under two glasses because I knew they were always in a hurry. If the
tip was a dime in one glass, the waitress, in her haste to get the table ready for the next
customer, would pick up the glass, the water would spill out, and that would be the end of
it. But after she does that with the first glass, what the hell is she going to do with the
second one? She can't just have the nerve to lift it up now!
On the way out I said to my waitress, "Be careful, Sue. There's something funny
about the glasses you gave me ­­ they're filled in on the top, and there's a hole on the
bottom!"
The next day I came back, and I had a new waitress. My regular waitress wouldn't
have anything to do with me. "Sue's very angry at you," my new waitress said. "After she
picked up the first glass and water went all over the place, she called the boss out. They
studied it a little bit, but they couldn't spend all day figuring out what to do, so they
finally picked up the other one, and water went out again, all over the floor. It was a
terrible mess; Sue slipped later in the water. They're all mad at you."
I laughed.
She said, "It's not funny! How would you like it if someone did that to you ­­ what
would you do?"
"I'd get a soup plate and then slide the glass very carefully over to the edge of the
table, and let the water run into the soup plate ­­ it doesn't have to run onto the floor.
Then I'd take the nickel out."
"Oh, that's a goood idea," she said.
That evening I left my tip under a coffee cup, which I left upside down on the
table.
The next night I came and I had the same new waitress.
"What's the idea of leaving the cup upside down last time?"
"Well, I thought that even though you were in a hurry, you'd have to go back into
the kitchen and get a soup plate; then you'd have to sloooowly and carefully slide the cup
over to the edge of the table. . ."
"I did that," she complained, "but there was no water in it!"
My masterpiece of mischief happened at the fraternity. One morning I woke up
very early, about five o'clock, and couldn't go back to sleep, so I went downstairs from
the sleeping rooms and discovered some signs hanging on strings which said things like
"DOOR! DOOR! WHO STOLE THE DOOR?" I saw that someone had taken a door off
its hinges, and in its place they hung a sign that said, "PLEASE CLOSE THE DOOR!" ­­
the sign that used to be on the door that was missing.
I immediately figured out what the idea was. In that room a guy named Pete
Bernays and a couple of other guys liked to work very hard, and always wanted it quiet.
If you wandered into their room looking for something, or to ask them how they did
problem such and such, when you would leave you would always hear these guys scream,
"Please close the door!"