10 Strangest Worlds In Star Trek
1. T'Khut
Most readers will be familiar with Vulcan, and many will be aware of its current or future name, Ni'Var. Yet how many will be aware of the planet's binary twin, T'Khut? This planet is strange because, depending on the day and the person speaking, it both exists and doesn't.
In the first televised episode of The Original Series, The Man Trap, Spock states that Vulcan has no moon. However, in Yesteryear, there is clearly something in the sky over Vulcan's horizon. This something would go on to be called T'Khut - depending on the source, and the time of the year.
T'Khut was 'accidentally' created by an animation artist during production on Yesteryear, one who evidently didn't receive the note that Vulcan should be moon-free. The theatrical edition of The Motion Picture also featured a moon or planetoid in orbit over Vulcan, but this was removed from the director's cut.
Fonata helped reconcile this error, first through print publication in 1975 via a series of stories and then later in Jean Lorrah's 1984 novel The Vulcan Academy Murders. Star Trek: Strange New Worlds finally re-canonised the planet in the first season, depicting the planet on a star chart, hovering in orbit of Vulcan.
The 1994 novel Sarek by A.C. Crispin further explains that the planet has different names for various times during the year - which also helps to explain the titles (including The Watcher) that it had been given in the course of its rather odd existence.