Throughout the entire time that the other man is there, Percy remains exceedingly polite. He's not about to cause a scene over something so trivial! He has manners.

It's not until he's left and Marta introduces herself that Percy unbends a little. (A very little.) He gladly accepts the handshake and reels off his disaster of a name. "Percival Fredrickstein von Musel Klossowski de Rolo III, but please, call me Percy."