A farmer and his girlfriend...
A farmer and his girlfriend were out for a stroll in the fields when they came across a cow and a calf rubbing noses."Boy," said the farmer, "that sure makes me want to do the same.""Well, go ahead," said his girlfriend. "It's your cow."

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."