Sprinkling parm or anything else on their food is just going to make them pickier. Trust me. Been there done that. Also Uni has pancreatitis so I can't add in more stuff anyway. But as far as cheeses go, parm is lower in cals than most other cheeses and has a more strong flavor.
Maybe they were doing the "whoop whoop whoop" move. Spreading the lovely cheese scent all over themselves and the rugs?