Can’t believe I got stumped by a three-year-old… AGAIN

Morris: “Mommy, guess what’s behind my back?”

Me: “A ball?”

Morris: “No! It has flat parts.”

Me: “A monster?”

Morris: “No! I TOLD you it has flat parts.”

Me: “A book?”

Morris: “Noooo.”

Me: “A picture?”

Morris: “Noooo.”

Me: “A piece of paper?”

Morris: “No. I’ll give you a hint. It’s white and fluffy.”

Me: “So it’s white and fluffy and flat?”

Morris: “Yep!”

… Can you guess what it was?

(Hint: Two minutes later he asks me, “Mmmphy! Gueff whap I haff i my mouf???”)