Fourth-order Green function calculations on very many core-ionized states of Mg-n clusters (n = 2,3,4) are reported. Among several interesting features the results reveal unusually strong low-lying satellites in the core ionization spectra of the clusters. These are absent in the respective atomic spectra and not observed in the spectra of typical molecules. A thorough analysis attributes these satellites to distinct interatomic processes. These processes comprise charge and energy transfer from one atom to neighboring atoms. Other cluster systems are briefly addressed.