Double or nothing : with the two and only Kelly twins / Johanna Hurwitz ; illustrated by Tuesday Mourning.

Enhanced descriptions from Syndetics:

What's the same about identical twins -- and what's different? Sleepovers, poetry projects, and new haircuts are in play as seven-year-old Arlene and Ilene start coming into their own.

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? Their tongues must be the same, so why do they like different kinds of ice cream? Why does Arlene wear pink nail polish while Ilene thinks it's silly? Why is Ilene sleeping soundly when Arlene is awake, wondering how she can be sure that she is Arlene, not Ilene? Revisit the funny, lovable characters from The Two and Only Kelly Twins and take a peek at the wonders -- and puzzles -- of being an identical twin.