Rarity receives a letter from Twilight that invites her to the next Gala. It also invites her to be the princess' fashion designer. When Rarity is on the train, her secret of Blueblood is let out, and she is teased for it. But when she arrives at Canterlot, Rarity needs to prove she likes stallions by marrying Blueblood. Problem is, Twilight has really deep feelings for Rarity.