Mary 's horse is Prince a ' fact ' that causes Scarlet to get jealous and worried that she 'll be replaced .
Prince is a white Thoroughbred stallion who is said to be the fastest horse ever to come to Horseland .
Mary 's horse is Prince , a white Thoroughbred stallion who is said to be the fastest horse ever to come to Horseland , a ' fact ' that causes Scarlet to get jealous and worried that she 'll be replaced .