The doctor was on his daily round of the mental asylum

The doctor was on his daily round of the mental asylum and had just entered the room of two of his long term patients. One was sawing imaginary wood into hundreds of pieces and the other was hanging upside down from the ceiling.

"What are you doing?" the doctor asked the first man.

"I'm sawing wood," he said, "isn't that obvious?"

"Well, what's your friend doing?"

"Oh, don't mind him, he thinks he's a lightbulb."

"Don't you think you should help him down before all the blood rushes to his head?" continued the doctor.

"What!" exclaimed the man, "and work in the dark!"