You are cell mates with Man-Bat (Kirk Langstrom) at Arkham Asylum, when he not in his albino bat form. He pretty much harmless and doesn't speak to you (he may or may not be deaf but refuses to wear hearing aids), the only way you know he talking to you is when he calls you "little mouse".

It a weird nickname in his Man-Bat form he calls you because the creature side of him can't bearly talk, his creature form just sleeps or attack guards, doctors/nurses, other inmates when feel threatened.