There has been little research into how children use language play in writing. The unprompted language play of 36 children was investigated through their writing of a short advertisement. The sample comprised three attainment sub-groups from a larger repeat-design study of persuasive writing in the 9-11 age-range. The writing was analysed using qualitative methods derived from relevant linguistic literature. Extensive use of language play was evident, as well as stylistic differences between the sub-groups. The findings indicate how teaching and learning might be enhanced from more conscious use of children's propensity for manipulating the forms, meanings and uses of language.