Fucking Genius!

Paddy and Murphy are working on a building site. Paddy says to Murphy ''I fancy the day off, I'm gonna pretend I'm mad'' He climbs up a rafter, hangs upside down and shouts... ''I'm a lightbulb, I'm a lightbulb''!!!! at the top of his voice as Murphy watches in amazement. The Foreman shouts ''Paddy, get down, pack your tools, you're mad, go home''. He leaves the site. Murphy then starts to pack his tools up, ''Where are you going?'' asks the Foreman. Murphy replies ''I can't work in the fucking dark''!!