Paddy and Murphy are working on a building site. Paddy says to Murphy,
"I'm gonna get the day off. I'm gonna pretend I've gone mad!" He climbs up the rafters, hangs upside down and shouts "I'm a lightbulb, I'm a lightbulb!"
Murphy watches in amazement.
The foreman shouts: "Paddy, go home. You've gone mad."
So Paddy leaves the site. Murphy starts packing is kit up to leave as well.
"Where do you think you're going?" asks the foreman.
"Well, I can't work in the friggin dark!" said Murphy.