This article examines language use amid a group of preschool Greek Cypriot children during their play time at home. Based on theories of performance and register-formation the article draws on ethnographic data in order to explore the way Standard Modern Greek and the Cypriot Greek are used in children's micro-interactions. The used methodology was case study research of a network of five children for a period of eighteen months and the main data collection techniques were participant and non-participant observation of the children during their play activities, with audio recordings and rich field notes. Data analysis pointed out that the two varieties were employed in a dynamic way by the children to form collaborations during play time, to enact social roles, to reflect cultural values and ultimately to add via their performances in register (re)formation.