KISS, SLAP

This could work for any rivalry. I choose tennis because I'm passionate about it:

A train is taking the greatest tennis players to the World Championships. Like most athletes who are constantly jockeying for the title of "Top Dog", they didn't like each other. So, it was quite a surprise to find Roger Federer, Rafael Nadal, Martina Navratilova, and Maria Sharapova sitting in the same box car. Each player barely said a word, focusing on the pending championship matches, strategizing on how to outplay the other.

The train passes under a tunnel and the lights go out. A kiss is heard, followed by a rather loud slap.

As the train exits the tunnel and the box car containing the tennis superstars is illuminated once more, each is looking at the other in shock, trying to figure out what had just happened.

Sharapova, the beautiful teenage sensation thinks that Nadal, the opportunist that he his, tried to reach over and kiss her when the lights when out, but missed, kissing Navratilova instead, causing Navratilova to slap him.

Navratilova, resigned that she is well beyond these childish shenanigans, thinks also that, as the lights went out, Nadal kissed Sharapova and was repaid with a slap.

Nadal, massaging his cheek, thinks that as the lights went out, Federer reached over and kissed Sharapova, but when Sharapova retaliated to this unwelcome advance, missed Federer and hit him, Nadal, instead.

Federer, being the number one player in the world by nearly 700 points and realizing that he got there by mostly outthinking his opponents, thought to himself: "Wow, I just kissed my own hand, slapped Nadal, and got away with it!"