A wipe-clean book for preschoolers full of friendly monsters to help children learn to write lower case letters A wipe-clean book for preschoolers full of friendly monsters to help children learn to write lower case letters. Pen control activities such as adding straight stalks to daffodils or curly antennae to an insect help children practise the shape of each letter in the alphabet, and the special wipe-clean pen can be used again and again.