by giving Jordon Mutch of Birmingham an invisible card 
http://uk.eurosport.yahoo.com/10032011/58/premier-league-ref-forced-brandish-invisible-yellow-card.html
If you want to see the video go to the link and it should come after some advert.
This reminds me of a time when my mate's dad was officiating a match and accidentally brandished a Mastercard
http://uk.eurosport.yahoo.com/10032011/58/premier-league-ref-forced-brandish-invisible-yellow-card.html
Referee Peter Walton was left red-faced during Everton's 1-1 draw with Birmingham City when he tried to book Birmingham's Jordon Mutch in the 40th minute.
Walton scrambled around his pocket for his yellow before quickly realising something wasn't quite right - that's right, he forgot to take his cards out from the dressing room.
Referees have to think quickly so Walton did the only thing he could do… he brandished an invisible yellow card to Mutch.
So while we give him a 0/10 for preparation, you have to give Walton at least an eight or a nine for improvisation.
The video of the hilarious incident should start up automatically in the picture box. (UK based users only).
The match ended in a 1-1 draw which was enough to take Birmingham out of the relegation zone.
Walton brandished three more yellow cards in the match, but they thankfully all came in the second-half when he had his cards safely back in his pocket.
If you want to see the video go to the link and it should come after some advert.
This reminds me of a time when my mate's dad was officiating a match and accidentally brandished a Mastercard
