Meet Cherokee and his stall mate Pixie.
Cherokee is showing us how he enhances the smell of his pony friend by curling his upper lip and exposing his front teeth. He holds this position for a few seconds and repeats.
"The behaviour facilitates the transfer of pheromones and other scents into the vomeronasal organ located above the roof of the mouth via a duct which exits just behind the front teeth of the animal." - Wikipedia
If you keep making that face, it might stay that way forever!