Ms. Mole's birthday is tomorrow and Elinor, Ari and Olive want to do something nice for her. Olive offers to bring in a cupcake -- nothing says happy birthday like a cupcake! But what if it gets squished in her backpack? The friends needs to figure out a way to keep the cupcake safe. Luckily, an evenful walk home from school provides some inspiration. First they watch as a stray ball from the playground lands on a turtle and bounces right off its shell -- no harm done. Then their friend Rollie Armadillo shows them his favorite game -- bouncing a ball on his shell. Finally they visit Ms. Llama at the snack stand for some coconut water, but the coconut is a tough nut to crack! The friends realize that the turtle, Rollie and the coconut all have something in common -- a shell! And that's just what they need to protect Ms. Mole's cupcake and stop the squish. Sidebars with more science facts and a key vocab word are interspersed throughout, and an activity at the end of the book teaches kids how to test the strength of an eggshell.

"From an episode of animated TV series Elinor wonders why"--Copyright page.