Complex sentence: Guy begins the story as a "Questerian" (Trekkie), who had had a small role as a disposable redshirt, greeting the actors familiarly although they don't recognize him.
Split into simpler sentences: Guy begins the story as a "Questerian" (Trekkie) who played a small role as a disposable crewman. He greets the actors familiarly although they don't recognize him.