How to get a red card even when you are not playing

This seemingly impossible feat was achieved by one Jean-Pascal Mignot - a substitute for Auxerre in their Champion's League game against Ajax.
His team were down 2 -1 and the game was almost over.
He then said something to the referee which was evidently not appreciated
So the ref walked up and showed Jean P M a yellow card.
Upon which Jean P M said a few more words.
Upon which said referee promptly showed him a second yellow card - and then the red - thereby sending off a player who was not actually on the field.
Incredible.