The studies in this volume show how multilingual learners use language play in second language acquisition to internalize sets of ‘voices’ (rather than decontextualized linguistic systems), namely complexes of linguistic and non-linguistic features incorporating the personalities of significant others. In sociocultural terms, these internalized heteroglossic voices become tools that learners can adapt and use playfully to enact chosen roles, stances, and identities in subsequent oral interactions. Different chapters explore these sociocultural constructs using different approaches, including variationist sociolinguistics, conversation analysis, translanguaging, and positioning theory.