Double or Nothing with the Two and only Kelly Twins

Arlene and Ilene love so many things about being identical twins. They like sharing a room, sharing friends, and wearing matching outfits. But they’re in different classes at school, and one twin has a scar that the other one doesn’t. One morning, their friends Monty and Joey point out a new difference that takes the sisters by surprise and gets them thinking: if they are identical twins, why are there differences between them at all?