The eyes are the mirror to the soul and if you keep an eye on people you will see the real character of a person emerge because none of us can hide for ever.
Mario has a big ego, he is vane, shallow, vengeful and a coward. If Bruce is annoying him so much why does he not confront him? Bruce's behavior is Bruce's, if Mario is unhappy with Bruce's behavior he should step-up to the mark and tell him.
Mario's nature is revealed every so often in his eyes, as is Louie's, and it aint nice, stay well clear is my advice.