In the beginning scenes of "School Horse" Carole's not wearing her earrings. In later scenes Carole has her earrings on.
When Prancer kills the snake, it's clearly made of rubber. In real life, the snake would have tried to bite Prancer when she first stepped on it.
When Carole is getting a running martingale for Prancer, the name tag for Belle can be seen. Stevie doesn't get Belle until "Found Horse Part 2".