The purpose of this paper is to exhibit clearly how the “graphical condensation” identities of Kuo, Yan, Yeh and Zhang follow from classical Pfaffian identities by the Kasteleyn–Percus method for the enumeration of matchings. Knuth termed the relevant identities “overlapping Pfaffian” identities and the key concept of proof “su- perpositions of matchings”. In our uniform presentation of the material, we also give an apparently unpublished general “overlapping Pfaffian” identity of Krattenthaler...