Two guys are in an office, the first turns to the second and says "I've got to get out of here, this place is doing my head in -- I'm going to take the day off."
The second guy turns to him and says "Well, how are going to do that?"
"Watch." And with that, he climbs a ladder. In a little while, their boss walks through the office and spots the ladder with one of his employees at the top of it.
He asks him why he's up there and the employee tells him he's a light-bulb. The boss tells him to get back to work and the employee says "I can't. I'm a light-bulb!" So the boss tells him to go home and get some rest and maybe go see the doctor.
As the employee leaves, his colleague joins him and the boss asks him where he's going. He turns around and says, "Well, I can't be expected to work in the dark, can I?!!"