Quatre brightens, as he notices him. "Marhaban," he says, approaching. "Trowa, wasn't it?"

One acquires a talent for remembering names early, and for a long time, when exposed to parties as often as Quatre has been. It helps than Trowa shares his name with the heir to L3.

(He doesn't remember much else, other than living on Earth, and a circus. Maybe something about elephants?)