The Galician definite article and direct object clitics exhibit allomorphy-like alternations which raise a number of questions for the morphology-phonology interface. This squib highlights inadequacies of allomorphic approaches to these alternations, outlining a novel way forward in which segmental changes apply to a stem in a fashion reminiscent of Celtic mutation. Differences between the article and the object clitic can then be ascribed to their prosodic weights, evident elsewhere in the language. Taken together, these findings expand our view of potential triggers for morphophonological alternations.