The Pope and Queen Elizabeth were standing on a balcony beaming at thousands of people in the forecourt below. The Queen says to the Pope out of the corner of her mouth, "I bet you a tenner that I can make every English person in the crowd go wild with just a wave of my hand." The Pope says, "No way. You can't do that." The Queen says, "Watch this." So the Queen waves her hand and every English person in the crowd goes crazy, waving their little plastic Union Jacks on sticks and cheering, basically going ballistic.
So the Pope is standing there thinking, "Uh oh, what am I going to do? I never thought she'd be able to do it." So he thinks to himself for a minute and then he turns to her and says, "I bet you I can make every Irish person in the crowd go wild, not just now, but for the rest of the week, with just one nod of my head." The Queen goes, "No way, it can't be done." So the Pope headbutts her.