A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

Bungee Jumping In Mexico
Two Americans decide to open a bungee-jumping business in Mexico.

They set up on the square of a small village. Bob jumps, bounces at the end of the cord, and flies back up by the platform. Jeff isn't able to catch his friend, but he notices he has a few cuts and scratches.

Bob falls again, bounces, and comes back up. This time, he is bruised and bleeding. Again, Jeff misses him. The third time it happens, Bob comes back pretty messed up - he's got a couple of broken bones and is almost unconscious. Luckily, Jeff finally catches him and says, "Holy cow, what happened? Was the cord too long?"

Bob looks confused and says, "No, the cord was fine... but what the heck is a pinata?"