A Cutie Mark is meant to represent the personality and special talent of each pony that has one. Cheerilee's flowers symbolize her desire to help her students bloom, and the smiles represent the cheer that she hopes to bring to their lives.

At least...that's what she tells everypony who asks.

[SEMI-SAD]

Luna has had enough of Celestia's games, and has found the perfect means of revenge. Using a long-forbidden spell, she transforms her sister into little more than a small filly, all so she could pull the greatest prank ever. Unfortunately, she soon learns that before you fool around with dangerous magic, you really need to read the fine print...

A sequel can be found here.

After seventy years building up one of the biggest companies in Equestria, Applebloom finally decides to go home. As she rides the train back to Ponyville, she revisits some of the moments in her life that have led her to this point and thinks about what could have been different.

Luna is on her way to visit Celestia, but hears her squealing for someone to 'stop!'

She walks in on Twilight on top of a red-faced Celestia, and the two of them react like guilty teenagers. Just what the buck is going on here?!