For me, I my area, we call people who take a lot of time to think as 'tubelights' (layman's term for linear fluorescent light), as the fluorescent lights would take some time to turn on (flickering on magnetic ballast). I have not heard of anything else like this. Do any of you know more sayings, phrases or jokes related to lighting?

Calling someone dumb a 'dim bulb'.

I don't remember exactly but there was some jokes about the bulb that comes in cartoons when someone gets an idea.