There's warmblood gelding at the barn that lolls his tongue out, rolls his eyes, shakes his head and moans like he's having a seizure. He apparently used to be extremely aggressive (charging around in his stall, snapping at whomever was feeding and kicking the walls) at feed time and when his owner got after him about it, he started doing this instead.
Since it's completely harmless (albeit really darn scary if you are feeding and unaware he will do this), his owner is ok with it. Over the years, he's basically given up since it doesn't garner him faster service or anything and now only does it if he is fed last. It's become the "party trick" of the barn and if anyone new is around, we'll feed him last just so they can see the spectacle.