I saw this on a website this week. Hope it's not in too bad taste..

A couple on their first visit to Spain stay at a nice hotel in a town where a fiesta is taking place and decide to eat their main evening meals at the hotel.
On the first night they don't know what to eat as the main course. They ask the waiter for some suggestions. He states that in fiesta time it's traditional to eat criadillas (bull's testicles). They're pretty adventurous people so they take his advice. In the end they quite enjoy the meal so later in the week they order the same dish. This time they're a little disappointed as the portion is quite a bit smaller. They complain to the waiter and say "What's the matter, were the bulls a smaller breed today."
"No." Replied the waiter. "Sometimes the bull doesn't always lose."