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."

Bulls Survive Tornado
There was a farmer who had a lot of live stock. He had
cows, horses, chickens, pigs, and bulls. One day a terrible
twister came and the man and his family were only saved by
throwing themselves in the nearest ditch. After it was all
over, he looked up to see that the house was gone. Saddened
by the loss, he went out to see if any of the animals had
survived. The horses, chickens, pigs, and cows were laid out
flat but the bulls were standing! The farmer was amazed and
asked them, "How is it that all the other animals are down
and you are still standing?" The bulls replied, "We bulls
wobble but we don't fall down!"