This poem is a funny way to encourage children to stay neat and tidy but if it was made more scary it could be a great starting point for a horror story. What would happen if small creatures really did start making a nest in your hair - or worse, inside your head? There are certain types of parasite that can live in the human body, some even eat brain tissue and affect people's behaviour. Terrifying stuff! Anthony McGowan wrote a book with a similar idea called Henry Tumour, about a boy called Hector whose brain tumour starts talking to him. The tumour - who calls himself Henry and has a distinct personality different to Hector's - encourages Hector to live life to the full... mainly because he is killing him! This is a dark and funny read about a serious subject.
If things living inside your head is too nightmarish to consider you could write a funny scary story. Tim Burton has written a collection of poetry called The Melancholy Death of Oyster Boy and other stories that contains some cautionary tales for young people, like what happened To The Girl Who Turned Into a Bed or how it all went wrong for Anchor Baby and Robot Boy. What annoys you about people that you'd write a crazy cautionary tale to stop them doing? Maybe someone who never listens and is always texting gets their phone stuck to their hands? Perhaps you can think of something more fitting!