For the last seven years I have been training both these mules in the dressage riding discipline. Dressage began as the highest level of equine training for cavalry movements and maneuvers for horses in the battlefield. This is now obsolete and has transformed into sport. So we have obsolete animals trained in an obsolete military discipline.
The teacup and the mule signify a sort of ghost of their own histories. In this video they perform a dressage dance interaction. The dance of the animate and the inanimate form the synergy of their obsolescence. A mule performs a piaffe (a calm, composed, elevated trot in place without forward movement) over a single unfired porcelain teacup and saucer. Eventually the cup will be trampled. The equine knows there is something underneath him. Not taught what to do with it, he tries to avoid it. Eventually the propulsion of the piaffe movement and the awkward attempts to avoid the cup causes him to lose track of where it is and he animates the inanimate at once by smashing it.
See this video play in LINKS, in the entry titled, "Ghosts".