THREADJACK!

I've always been curious about this: what is required to rent a car in Europe* when vacationing? I know they drive on the right or wrong side of the road and the signs are completely different. Do you have to take a test or something? Are you required to drive while holding a cell phone to your ear there, too?

Signed, Clueless.

* Actually, I'm interested in learning the answer for all locations.