Olek is six years old and lives above a bakery. Today he goes to kindergarten with a new backpack. The kitchen smells of warm buns and cocoa. The backpack lies on a chair and suddenly giggles. The dog Keks freezes and lifts one ear. "Did you hear that?" asks Olek, a little surprised. The backpack shakes like jelly and giggles again. Mum helps put on her jacket and shoes. Olek puts the banana and pencil case in the backpack. After a while, he smacks something and quietly mutters. "Don't mlinkle, banana," whispers Olek to the zipper. Squeaks and funny hiccups are heard from the backpack. With his tail, Keks knocks on the door like a drum. On the cage, the echo answers: hi-hi, pi-pi. Mrs Ela and the whole group are waiting in the hall. Olek sits down and puts his backpack under a chair. The backpack jumps up and makes a strange squeaking sound. The crayons buzz as if they are doing a concert at the bottom. "What kind of concert is that?" asks the lady quietly. The children giggle and lean closer. Olek grabs the zipper and slowly lifts it. At that moment something springy pops up....