This paper documents the occurrence of form variability through diminutive ‘wordplay’, and examines whether this variability facilitates or hinders morphology acquisition in a richly inflected language. First, in a longitudinal speech corpus of eight Russian mothers conversing with their children (1.6–3.6), and with an adult, the use of diminutive word forms was shown to be pervasive in Russian child-directed, but not adult-directed speech. Importantly, all of the mothers were shown to routinely engage in alternating uses of diminutive and simplex forms of the same nouns within the same conversational episodes. Second, an elicitation experiment was conducted which tested 24 children's (2.7–4.2) productivity in inflecting novel nouns for case. By varying whether children heard the novel nouns in diminutive form, simplex form or both, we show that children benefit from the introduction of words in multiple forms (i.e. showing fewer case-marking errors in this condition). We suggest that pragmatically motivated form variation in child-directed speech (CDS) may have beneficial effects for acquiring richly inflected languages.