Rainbow Dash's stomach hurts and she is not happy about it. She refuses to go to the doctor because she knows that her friends must have a remedy.
She goes to Twilight first. Nothing. She then goes to Applejack. Still nothing. She goes to Pinkie. More nothing. She goes to Rarity. She wished she hadn't.
She then goes to Fluttershy and realizes what her problem is and knows how to fix it.