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 problem with teeth
This minister just had all of his remaining teeth pulled and new dentures were being made.

The first Sunday, he only preached 10 minutes.

The second Sunday, he preached only 20 minutes.

But, on the third Sunday, he preached 1 hour 25 minutes.

When asked about this by some of the congregation, he responded this way.

The first Sunday, my gums were so sore it hurt to talk.

The second Sunday, my dentures were hurting a lot.

The third Sunday, I accidentally grabbed my wife's dentures... and I couldn't stop talking!