I describe and analyze the morpho-phonology of the English diminutive suffix /-i/, as in doggy, birdie, horsie, and so on. My first goal is to argue that unlike most other diminutives in English this suffix is productive, though subject to a phonological constraint. Specifically, I show that this suffix must be adjacent to a stressed syllable—a requirement that motivates exceptional truncations. I propose that thesefacts provide a clear instance of a morpheme-specific phonological constraint. My second goal is to examine how this diminutive interacts with nouns that normally have irregular plural forms. I show that this diminutive can block irregular plural morphology, but optionally allows the persistence of plural ablaut. I explain these facts using an analysis in which morphological rules require adjacency between the triggering node and the affected one, along with a proposal that the English diminutive /-i/ is an adjunct/modifier which can be attached late in the derivation.