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 man was walking in the street when he heard a voice...
A man was walking in the street when he heard a voice: "Stop! Stand still! If you take one more step, a brick will fall down on your head and kill you."The man stopped and a big brick fell right in front of him. The man was astonished. He went on, and after awhile he was going to cross the road. Once again the voice shouted: "Stop! Stand still! If you take one more step a car will run over you and you will die."The man did as he was instructed, just as a car came careening around the corner, barely missing him."Where are you?" the man asked. "Who are you?""I am your guardian angel," the voice answered."Oh yeah?" the man asked..."And where were you when I got married?"