Celestia tends to be cranky when she's stressed. So when Discord wakes her up to complain about feeling like Fluttershy has been ignoring him. She doesn't take it well. After a heated argument, a magical mishap between the two causes them to regress in age.

You are Gene, a twelve year old pegasus filly who was orphaned and taken in by Fluttershy. And when a magical mishap happens between Celestia and Discord, you now have to deal with an even more immature form of Discord (assuming it's possible for Discord to be more immature than he already was). You and Discord never got along well in the first place. And you realize that just because you're now bigger and stronger than he is now, he's still a pain in your flank.

And between Dissy, your'e adoptive mother Fluttershy now a single mother taking care of three children, and Anon's own issues with Tia, life is certainly not going to be the same.

Inspired by Moonie Shorts by Eighth. Anon's point of view can be found in Little Tia.