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."

An Unusual Vet
There was once an aspiring veterinarian who put himself through veterinary school working nights as a taxidermist.
Upon graduation, he decided he could combine his two vocations to better serve the needs of his patients and their owners, while doubling his practice and, therefore, his income.

He opened his own offices with a shingle on the door saying, "Dr. Jones, Veterinary Medicine and Taxidermy -- Either way, you get your dog back!"