While Storm Strike and Feather Fieldgoal are as different as can be when it comes to personality, the same cannot be said about their appearance. They’re identical twins, and as young fillies they looked almost exactly alike. Anypony with a keen enough eye could spot their slight variations in mane color and hairstyle, but to many they looked like the same pony.  
At one point, the girls decided to use their identical looks to their advantage for the prank of the year. Miss Cheerilee was on leave for “personal reasons”, so their substitute was an aging stallion with bad eyesight and slight color-blindness. He always relied on the fillies responding to their own names to tell them apart. Otherwise, he would mix them up all the time.  
This is exactly what would make Storm and Feather’s prank work. They made a plan to spend the entire week in each other’s places, going by each other’s names and attending to each other’s schoolwork and extracurricular activities. They even made a pact with all of their classmates to play along with it. And it worked! The teacher was fooled for almost the whole week…until that Friday, when Storm accidentally responded to her own name. Whoops.  
Despite the prank ending on a less than successful note, it was fun for the sisters to try and fill each other’s horseshoes, even if it meant doing things they normally wouldn’t. Storm and Feather really gained a new understanding of each other’s interests and personalities as they tried to imitate each other. Even into adulthood, they like to look back, laugh over the prank, and reflect on how much they bonded.