A Northerner, a Southerner and a beautiful woman are sitting together in a train going through the Rockies.
Suddenly, the train goes through a tunnel and, being one of the older-style trains with no carriage lighting, it goes completely dark.
Suddenly there's a kissing sound, followed by the sound of a really loud slap.
When the train comes out of the tunnel, a beautiful woman and the Southerner are sitting as if nothing happened while the Northerner has a nasty red slap mark on his face.
The Northerner thinks, "The Southern fella must have kissed the beautiful woman and she missed him and slapped me instead."
the beautiful woman thinks, "The Northern fella must have tried to kiss me and actually kissed the Southern fella and got slapped for it."
The Southern fella says to himself, "This is great. The next time the train goes through a tunnel, I'll make another kissing noise and slap that Northerner again!"