Princess Celestia always thought she knew how her kingdom worked. The Unicorns used magic specialized to their jobs. Pegasi flew in the sky and handled the weather. And Earth ponies... Earth ponies... uhhmmm...
Huh. Maybe Princess Celestia didn't know everything about her ponies after all.
Princess Celestia realized this after Applejack came to speak with her about a tax unfair to Earth pony farmers. It was during their conversation that Celestia realized she needed help.
Huh, isn't that odd Princess Celestia has had to leave on emergency business, leaving Luna to raise and set the sun? And hey, is that a new pony living and working at Sweet Apple Acres? I think her name is Sunshine Meadow. Surely, it's just a coincidence. Surely.

When your life is as dull a gray as the world that surrounds you, the mundanities can make it all seem meaningless. Sometimes all we need is a little color -- or six -- to reintroduce us to what truly makes life worth living.

*6-16-2017 Edit, added Rainbow Dash tag because it triggered knighty.*

Rarity can't get anything done when an old question comes back from her days as a blank flank filly, so she searches for her answer.

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.

No one has ever questioned how a zebra came to live on the fringes of Ponyville. Much less why that zebra constantly speaks in fluid rhymes. When someone finally asks, Zecora recounts the whole tale of why she rhymes and just how it brought her to Ponyville.

Written mostly from first person Zecora's perspective, except for when talking directly to Shadow and not telling the story.