- Seattle Slew: Known for his fiery temperament, Seattle Slew could be challenging to handle, especially during his early training days. He required patient and skilled handling to bring out his best qualities.
- Secretariat: While Secretariat was an incredibly gifted athlete, he also had a strong and independent personality that made him difficult to train. He responded poorly to harsh methods and required a gentle touch to achieve the best results.
- Man o' War: Considered one of the greatest racehorses of all time, Man o' War was known for his high energy and spirited nature. He was quite opinionated and could resist attempts to control him if he didn't agree.
- Nureyev: Renowned for his beauty and athleticism, Nureyev was a demanding and temperamental horse. He required highly skilled and experienced jockeys to fully understand and manage his quirks on the racetrack.
- Temperence Hill: A horse with an unpredictable and challenging personality, Temperence Hill could be prone to violent outbursts and had to be handled with extreme caution.
- Zenyatta: Although successful on the track, Zenyatta was known to have a mind of her own. She could be stubborn during training and presented unique challenges for her handlers and jockeys.
- Alysheba: Despite being a formidable competitor, Alysheba could be quite temperamental and difficult to manage off the track. He required careful handling to avoid potential behavioral problems.
- War Admiral: Known as the "Sea Biscuit" of his time, War Admiral had a strong personality and could be difficult to control, particularly during his younger days of racing.
- Sham: Sham, a rival to Secretariat, was not known for being the most cooperative horse in training. He required an expert jockey like Bill Shoemaker to bring out his best performances.
- Ruffian: Ruffian, a talented filly, was known for her fierce spirit and determination on the track. She could be physically demanding and needed skilled riders to manage her energy and power effectively.