You probably know this already. But before seeing the boffo Juneau, Alaska, production of Oklahoma! I hadn't really focused on it, so I figured it was worth sharing the point.
Where did PSY's horse-riding dance in Gangnam Style come from? It certainly seems as if it might have come from Agnes De Mille's choreography for the dream-ballet sequence of Oklahoma! as shown below. Skip to time 8:25.
If you would like to hear Agnes De Mille discuss the thinking behind this sequence, go here. And if you would like to see a far more explicit matching of PSY and Agnes De Mille, try this. It's the dances from another possible De Mille source of Gangnam Style, Aaron Copland's Rodeo - but set to PSY's music.
"Straight," non K-Pop version of Rodeo is here. Submitted in the interest of cultural understanding.