As we saw at last summer's World Cup, when English referee Graham Poll showed three yellow cards to Croatian Josip Simunic before sending him off, the guys in the middle sometimes loss track of their bookings.
In a Scottish Premier League game last weekend, referee Alan Freeland actually asked Falkirk midfielder Stephen O'Donnell, upon showing him yellow in the second half, if he had already been cautioned.
So how did O'Donnell react? With honesty and sportsmanship? No way.
"The ref asked me the most stupid question ever: 'Have you been booked already?' I don't know what he was expecting me to say but I said 'no'," explained O'Donnell, who then attempted to tell his coach to sub him before Freeland realized his mistake.
But a fourth official alerted Freeland, who belatedly sent the liar to the locker room.