Even small delays in Japan's much-vaunted bullet trains are rare, and more unusual still are snakes on board holding up the speedy "shinkansen" services.It was unclear whether the cold-blooded commuter was venomous or how it ended up on the train, and there was no injury or panic among passengers, a spokesman for Central Japan Railway Company told AFP Shinkansen customers can bring small dogs, cats and other animals, including pigeons on board -- but not snakes.