"Burninating the countryside... burninating the peasants... burninating all the peoples... and their thatched-roof COTTAGES! THATCHED-ROOF COTTAGES!! And the Trogdor comes in the NIIIIGHT!!!"
Five years of cheap thrills in the big city has left Sweetie Belle in bad debt with dangerous ponies. Forced to pay up, she returns to Ponyville to seek money from an estranged sister she loathes with a passion.
Marble enjoys sculpting rocks, but her father doesn't see that as a lucrative or useful way to live one's life. He thinks she needs to get married. Marble doesn't want to, and will go to great lengths to ensure she won't have to.
Octavia is just a bum cellist living in what passes for the Ponyville slums. She is forced to play at birthday parties and small events until she is given an unexpected shot at returning to the big time. Oh, and she's a were-shark. Can't forget that.