Real-life Japanese thoroughbred racehorse, famous for winning the the Japanese Triple Crown and being the first undefeated Japanese Triple Crown. He was inducted into the Japan Racing Association (JRA) Hall of Fame in 1987.
Rudolf has a predominantly bay coat with a prominent white crescent-shaped facial mark near the top of his head. Three of his legs are completely black starting from the knee down; his left hindleg is black from the upper knee but shifts color to white after the cannon (i.e. the metatarsals. May look like the lower knee or ankle for people unfamiliar with horse anatomy).
Or, in equivalent humanoid character terms, he has black 'thighhighs' (i.e. "stockings", to use the horse fur pattern terminology) on all four of his legs, plus an additional white ankle "sock" on 'top' for his left hindleg.
