From the Horse's Mouth (Sabrina The Teenage Witch)

A horse is a horse....

Staying on a horse is hard, and learning to ride is even harder. Especially when, for her Phys Ed beginner equitation class, Sabrina is assigned to ride a cranky and lame critter. His name? Mission Impossible. Uh-oh.

If Sabrina can¹t learn basic horsemanship in the next two weeks, snobby classmate Debra will snicker, and worse, Sabrina¹s horse might be sold to a run-down rental stable. There¹s no time for horsing around. Looks like this might be an impossible mission for Sabrina, until Mission Impossible starts talking!