This paper examines so-called “Person Case Constraint” (PCC) effects. These are ordering restrictions on co-occurring clitic pronouns, where only certain person combinations are felicitous but the possibilities vary cross-linguistically. Taking the South Slavic languages as a point of departure, an account is developed in terms of person feature spreading from a high Appl(icative) node to underspecified clitic pronouns. It is argued that 3rd person is the absence of person features, hence there is no PERS(on) node per se, and that person can be characterized in terms of PART(icipant) and AUTH(or). It is further argued that languages may differ in terms of how these two features are arranged, accounting for additional systems. Finally, speculations are offered on how feature spreading enlightens PCC violation repair strategies.