Octavia loves old music. Celestia was alive at the height of its popularity. So Celestia's personal assistant, Pinwheel, arranges a meeting of the minds. Except now Pinwheel is the odd pony out.
When Derpy fills out her tax return, she finds that she owes quite a bit of money. However, she seems to have an alternative way of settling the debt. She might even have fun.
Pinkie Pie's 'cousin Horsey' comes to visit, but Twilight Sparkle is suspicious. Sometimes we wear masks to hide our true feelings... sometimes that can be taken literally.