Arex was a three-armed, three-legged alien who served as navigator of the Enterprise in Star Trek: The Animated Series.
Arex was a lieutenant who served as navigator aboard the Enterprise in Star Trek: The Animated Series. He came from the planet Edo and had three arms and three legs, a body that would have been very hard to show in live action but was easy to draw in animation. He was voiced by James Doohan, who also voiced Scotty and many other characters.
Arex took the navigation station beside Hikaru Sulu, filling the role of Pavel Chekov, who did not appear in the animated series. He was a calm and capable officer and took part in many bridge scenes and landing parties during the show's two seasons. Along with the Caitian M'Ress, he was one of the two non-human bridge officers created for the animated series.
Arex is one of the best-known characters to come out of the animated series and shows how the format let Star Trek expand the variety of its crew, an idea later series continued.