Hard back book.
This is incredibly embarrassing but ...Polar Bear has lost his underwear. Where could it be? Is that Polar Bears underwear? On the page is a die-cut pair of underwear. Turn the page, and the wearer is revealed! No, that isn't Polar Bears underwear. Its Zebras underwear the pair has colourful stripes. What about that itty bitty pair? Maybe ...actually, no its Butterfly's, who is flying high in a mini pair of undies.