Wrong Again (1929)
Among the horses stable hands Stanley and Oliver are tending is a thoroughbred named "Blue Boy." But when they overhear two men talking about a $5000 reward for the return of the stolen "Blue Boy," they miss the part about it being the painting, not the horse. They get the owner's address, though, and bring the horse along to claim the reward. They wonder at the rich man's instructions to put "Blue Boy" on the piano but, Oliver explains, "these millionaires are peculiar."