A ubiquitous officer aboard Captain Kirk's Enterprise, played by Eddie Paskey, who turns up at the helm, in engineering and in security details throughout the first two and a half seasons of the original series.
Lieutenant Leslie is the most frequently seen background crewman of the original Star Trek. Played by Eddie Paskey, he first appears in Where No Man Has Gone Before and goes on to appear in dozens of episodes, usually without dialogue.
He has no fixed post. He is seen as relief helmsman, at the engineering station on the bridge, in the transporter room and as a security guard on landing parties, and he occasionally sits in the command chair.
In Obsession he is among the security men killed by the vampire cloud on Argus X, yet he is back at his station in later episodes with no explanation, a continuity slip that has become a favourite piece of fan lore.