Ian receives ventriloquists' dummy Slappy as a twelfth birthday gift, and when Ian's annoying cousins recite the magic words that bring Slappy to life, the doll unleashes pranks that are blamed on Ian.

As spring arrives on Gardam Street, there are surprises in store for each Penderwick, from neighbor Nick Geiger's expected return from the war to Batty's new dog-walking business, but her plans to use her profits to surprise her family on her eleventh birthday go astray.

After her twelfth birthday, Rory checks off a list of things she is finally allowed to do, but unexpected consequences interfere with her involvement in the movie being shot at her school, while a weird prediction starts to make sense.

It's Nikki's birthday, and it is up to her whether it is a blast or a bust.

For their twelfth birthday Willow's mom is planning a combined birthday party for Willow and her twin brother, Winston--boys and girls will both be invited for a Halloween masquerade, but soon the games threaten to get out of hand.

After celebrating their first nine same-day birthdays together, Amanda and Leo, having fallen out on their tenth and not speaking to each other for the last year, prepare to celebrate their eleventh birthday separately but peculiar things begin to happen as the day of their birthday begins to repeat itself over and over again.