Today Pororo and friends are playing hide and seek. It's Poby's turn to find his friends. Harry had to change his hiding place because Pororo hid there before him. So Harry sang a song to reveal where Pororo was hiding. Pororo decides to play a trick on Harry. Pororo tells Harry to hide inside a mailbox and locks him in. Pororo goes into the house and hides. But everything seems a bit larger than usual today. Oh dear, what has happened? Pororo shrunk!