This talk presents an overview of VRK mutation in a group of Austronesian languages of West Papua, Indonesia. VRK mutation is a phonological pattern in which the segments /ß/, /r/, and /k/ behave unusually in clusters, usually surfacing as [mb], [nd], and [ŋg], respectively. This is typologically unusual for two reasons. First, phonological rules generally target a natural class rather than a random assortment of segments, and /ß, r, k/ appears to be the latter. Second, the change is not phonetically improving – in some languages, even a sequence of two identical VRK segments, such as /rr/, will trigger mutation, in this case to [nd]. Bach & Harms (1972) call patterns like this one “crazy rules”, and a small set of examples have been documented. VRK mutation stands out from these previously known examples and upends our expectations of what such a rule should look like. While most such patterns diverge from typical phonological typology on only one dimension, VRK mutation does so in two. And while all other documented unnatural rules are restricted to a very small set of undergoer languages, VRK mutation is widespread, appearing in a group of (at least) 20 Austronesian languages which diverged from one another roughly 3000 years ago. In this talk I survey the forms VRK mutation takes and the morphological structures it affects across these 20+ languages, based on data from original fieldwork and both published and unpublished sources, to give a typology of the pattern. I then give a historical account of how it arose, tracing the development of modern /ß, r, k/ from earlier *b, *d, *g in a canonical case of historical rule
reversal.