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 responsible applicant
Employer to applicant: "In this job we need someone who is responsible." Applicant: "I'm the one you want. On my last job, every timeanything went wrong, they said I was responsible."