Or people. Or sportspeople.
On my way in to work, the car in front of me had a license plate frame labeled "12th fan, strong and proud", or something very similar.
Shouldn't that be "12th MAN"?
So, I googled it when I got in, in case there was something special about being the 12th fan that I don't understand. And, sure enough, there are numerous Seattle Seahawks hits about being the 12th fan. Did somebody screw up when they did the promotion, and now it's caught hold in the popular consciousness?