We’ve all said it. It’s a great way to express incredulity at a stupid question. The problem is, it turns out, the Pope isn’t actually Catholic. Awkward.
The short version is as follows: (1) The person we think is the Pope isn’t actually the Pope; (2) Another guy, who IS actually the Pope, well it turns out he’s not Catholic.
We’ll have to stick to the other expression about bears and outdoor ablutions.