"Telephone terror - is Harold there?" joke
This was a practical joke my cousins came up with for a good laugh.
There just happened to be six of us together with nothing to do. So we got the phone book, picked out a number at random, and the first person dialed.
When the person answered, my cousin asked for a random name - let's say, Harold.
"No Harold here", came the answer.
"Are you sure there's no Harold there?" she insisted.
The stage was set.
About half an hour later, another cousin called the same number and asked for Harold.
Over the course of two hours, three more of us called the same number, asking for the same Harold, while this poor man on the other line had to tell each of us the same thing, and getting more and more frustrated each time. (Of course, since he assumed we were totally unrelated in any way, he wasn't blowing over or anything.)
Finally, I called about an hour later.
"Hi, this is Harold. Did I get any messages?"