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."

A young executive was leaving the office...
A young executive was leaving the office at 6pm when he found the CEO standing in front of the company shredder with a piece of paper in hand.

"Listen," said the CEO, "this is very important, and my secretary has already left. Can you make this thing work?"

"Certainly," said the young executive. He turned the machine on, inserted the paper, and pressed the start button.

"Excellent, excellent!" said the CEO as his paper disappeared inside the machine. "I'll just need one copy."