How many psychiatrists does it take to change a light bulb?

Only the one. It's hardly an arduous task.

Where do you go to weigh a whale?

A fishing port would be the best place, as they have the appropriate craneage - although as whaling is illegal in most places you would have to take it to Japan (submitted by Druid of B3ta)

How does Bob Marley like his doughnuts?

Contrary to popular belief, he wasn't actually a fan.