A Big Glass of Water
A man goes to the doctor and tells him that he hasn't been feeling well. The doctor examines him, leaves the room and comes back with three different bottles of pills. The doctor says:

"Take the green pill with a big glass of water when you get up. Take the blue pill with a big glass of water after lunch. Then just before going to bed, take the red pill with another big glass of water."

Startled to be put on so much medicine the man stammers:

"Jeez doc, exactly what's my problem?"

Doctor says,

"You're not drinking enough water."

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."