You know you're a fan when you see a white DVD with a large eye on it in a store, and from thirty feet away can tell that that eye is Paul McCartney's eyes.
Or apparently, that's how you know you're a fan, according to my brother. I'm guessing that ANYONE on this forum could do it. Though that doesn't prove much, does it?
You also know you're a fan when you spend thirty bucks on the Beatles Trivial Pursuit even though you know full well that the ONLY person you could play with lives on the other side of the country.