Star Trek: 10 Alien Races That Only Appeared Once
2. Horta
This is one of the great, CLASSIC creature designs from The Original Series and in essence it's a bloke lying on a board with some wheels covered in foam. Amazing.
But don't let that put you off because this silicon-based lifeform was the first serious non-humanoid alien Star Trek attempted. She posed a threat to the miners on Janus VI leading Spock to mindmeld with the mother creature in one of the first season's most memorable scenes. For an era without the wonders of CG, this was a big step forward in imagination. Both the Gorn and the Tholians would receive upgrades from the visual artists on Enterprise but the Horta would not be as fortunate.
This was as high-concept an alien as a 1960's TV budget could allow and still expressed everything that Star Trek was about. She added herself ably to a list of misunderstood creatures that ultimately weren't as evil and obsessed with killing as the story suggested.
While the Horta has never turned up again in an episode of the show, it has been utilised in Star Trek novels as a crewmember on at least two occasions; the USS Darwin in Dyson Sphere and more recently aboard the USS Titan in Taking Wing.