Rarity is watching Sweetie Belle while their parents go an vacation but the two sisters quickly run into problems as Rarity's uptight attitude conflicts heavily with Sweetie Bell's playfulness and eagerness to please her older sister. Sweetie Belle tries her hardest to please Rarity but all her efforts just end up irritating her instead. Sweetie Belle then draws a picture and shows it to Rarity(we see the picture surrounded with gems). Rarity takes one look at the picture and loses control. When Rarity is out collecting more gems, Apple Bloom shows Sweetie Belle the flyer for the Sisterhooves Social.
Later on, Sweetie Belle shows Rarity the flyer. Rarity says it wouldn't be very "clean". Sweetie Belle and Rarity then get into an argument. It ends with them both agreeing they don't need a sister. Sweetie Belle leaves the boutique.
Sweetie Belle is seen at Sweet Apple Acres with Apple Bloom and Applejack. Sweetie Belle watches as the sisters have fun together while getting their hooves dirty.
Meanwhile at the boutique Rarity sees the drawing that Sweetie Belle drew of the two of them and decides that she needs her little sister after all. When Rarity tries to convince Sweetie Belle to come back with her Sweetie Belle refuses and says that she would rather have Applejack as her sister instead. Sweetie Belle also suggests that Rarity try to be more like Applejack.
On the day of the social Apple Bloom offers to lend Applejack to Sweetie Belle, emphasizing that it is only for one day.
During the first part of the race Applejack falls into a pit of mud and has to continue the rest of the competition covered completely in mud. Sweetie Belle has a wonderful time and is very surprised to find that when Applejack fell into the mud she stayed there and that Rarity was the one that had finished the race with Sweetie Belle.
Sweetie Belle and Rarity reconcile and with the help of Spike composing a letter to Princess Celestia about what they have learned.