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."

Airplane Trouble
An airliner was having engine trouble, and the pilot instructed the cabin crew to have the passengers take their seats and get prepared for an emergency landing.

A few minutes later, the pilot asked the flight attendants if everyone was buckled in and ready.

"All set back here, Captain," came the reply, "except one lawyer who is still going around passing out business cards."