When your favorite team makes the World Series, it can be difficult to tell the true fans from the bandwagon ones. If you were to go, say, to a packed San Francisco bar like The Brick Yard to watch a game, you might be mistaken for a bandwagoner. Solution: screen print up some clever t-shirts for you and your boyfriend. Sexual innuendo is funny!
Perhaps related, here's a 2012 poem from the Baseball Sexual Frustration tumblr:
I wanna take off brandons belt
buster can bust my posey
i just lincecame
i wanna make tim lincecum
i like my posey shaved & my wilson hairy
brandon can take of my belt