Mum and Dad don't see him, but he's definitely there - a cheeky purple monster, with blue and spiky hair. He's the one who does those things, that no one seems to do. Who smudged toothpaste on the tap? It wasn't me. Was it you? From mischievous behaviour to a monster feeling grand! And kids that end up second-best ... oh-no! This isn't what they planned!