In head-marking languages, pronouns may appear as bits of morphology on a verb or other head. Sometimes these look like agreement markers (Bresnan and Mchombo) and sometimes they look like disagreement markers (Hale and McCloskey).
Joan Bresnan and Sam A. Mchombo (1987) ``Topic, Pronoun, and Agreement in Chicheŵa,'' Language 63, 741-782.
James McCloskey and Kenneth Hale (1984) On the Syntax of Person-Number Inflection in Modern Irish. Natural Language and Linguistic Theory 1.487-533.
*Andrews, Avery D. 1990. Unification and morphological blocking. Natural Language & Linguistic Theory 8.507-57.