He thinks he's a light bulb
A doctor of psychology was doing his normal morning rounds when he entered a patient’s room. He found Patient #1 sitting on the floor, pretending to saw a piece of wood in half. Patient #2 was hanging from the ceiling, by his feet.
The doctor asked patient number 1 what he was doing. The patient replied, “Can’t you see I’m sawing this piece of wood in half?”
The doctor inquired of Patient #1 what Patient #2 was doing. Patient #1 replied, “Oh. He’s my friend, but he’s a little crazy. He thinks he’s a light bulb.” The doctor looks up and notices Patient #2’s face is going all red.
The doctor asks Patient #1, “If he’s your friend, you should get him down from there before he hurts himself?”
Patient #1 replies, “What? And work in the dark?”