Al and Joe are bungee-jumping one day.
Al says to Joe,"You know, we could make a lot of money running our own
bungee-jumping service in Mexico." Joe thinks this is a great idea, so they
pool their money and buy everything they'll need; a tower, an elastic cord,
insurance, etc. They travel to Mexico and begin to set up on the square. As
they are constructing the tower, a crowd begins to assemble. Slowly, more
and more people gather to watch them at work.
When they had finished, there was such a crowd they thought it would be a
good idea to give a demonstration.
So Al jumps. He bounces at the end of the cord, but when he comes back up
Joe notices that he has a few cuts and scratches.
Unfortunately, Joe isn't able to catch him,and he falls again, bounces and
comes back up again.
This time, he is bruised and bleeding. Again Joe misses him.
Al falls again and bounces back up. This time he comes back pretty messed
up-he's got a couple of broken bones and is almost unconscious.
Luckily, Joe finally catches him this time and says,"What happened? Was the
cord too long?"
Barely able to speak,

Al gasps, "No, the cord was fine, but what's a pinata?"

another good trick is to wait till the person is half way through starting to jump and yelling "wait not yet i forgot to tie the rope"

Here's another one on this topic:
What does bungee jumping have in common with prostitution?
If the rubber breaks, you could be in for some real trouble !