You open the door and jump on your bike. You grab your backpack, and stuff the mini version of you inside it, at the very bottom, so no-one can see it.
Ow! You feel a sharp pain in your back, like a book is pressing on it. You decide to ignore it, and ride to Mr Ollie's toy shop.
On the window, there is a sign which says: MR OLLIE'S TOY SHOP. SPECIALISES IN MAKING VOODOO DOLLS. JUST BRING IN A PICTURE AND WE'LL MAKE IT!
Hang on, you think. Voodoo Dolls? Wouldn't that mean ... you quickly grab your backpack and throw out all the books. There, at the very bottom, was your voodoo doll ...