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."

Bosses versus workers
When I take a long time, I am slow.
When my boss takes a long time, he is thorough.

When I don't do it, I am lazy.
When my boss doesn't do it, he's too busy.

When I do it without being told, I'm trying to be smart.
When my boss does the same, that is initiative.

When I please my boss, that's brown-nosing.
When my boss pleases his boss, that's co-operating.

When I do good, my boss never remembers.
When I do wrong, he never forgets.