Princess Celestia is high and mighty in a lot of ways, motherly and mentor-like in more. But her proteges have almost always been unicorns, with one or two pegasi, and not one earth pony in all of her over 1000 years of life. When Applejack, staying true to her Element of Honesty, even with the Princess, bluntly states that Princess Celestia understands little of what it's like to be an earth pony, the princess realizes the flaw in her understanding of her subjects. Turning to a newly reformed old friend, Celestia begs to be an earth pony for a day. What happens, nopony could have guessed.