You're a fan when you do the following things at an amusement park:
-Count the people wearing Beatles t-shirts (got 6 yesterday)
-Freak out when you find that there's a band there that plays Beatles songs
-Buy a Beatles picture that they're selling there.... even though you already don't have enough room for Beatles stuff you already have
And of course, if you're listening to Breakfast With The Beatles on a local radio station as you type this.