The Man Trap is a typical "space monster" episode with a twist; the "monster" in question can assume any form it wishes, usually conforming to the semblance of someone from its intended victim's past, and along with the salt it requires for its nourishment, it also needs love.
Space monsters need love, too
I have mixed feelings about this episode. The creature's need for love and the fact that it's the last of its kind makes it something more than just a two-dimensional threat to the crew and also gives its death some poignancy. Professor Crater's pathetic love for the creature even though it killed his beloved wife and then took on her form (with his knowledge) also gives this episode a touch of pathos. However, the way this episode was structured felt "wrong" to me; the fact that there is something odd about "Nancy Crater" is immediately revealed to the audience and Professor Crater's clumsy and brusque attempts to get the Enterprise crew to leave posthaste (albeit after leaving behind a sizable ration of salt tablets) and leave him to his own private fantasy clues the viewer in on the fact that:
This, in my opinion, robs the episode of much potential suspense and mystery. What's the point of having a homicidal shape-shifting creature on the loose if you don't, at least, make an attempt to pull one over on the viewing audience? Isn't that the obvious thing to do? Or am I speaking with the benefit of more than forty years of evolution in the art of story-telling via the media of television and film behind me?
The Man Trap marks the first appearances of Dr. Leonard "Bones" McCoy and Lieutenant Nyota Uhura. Dr. McCoy, as played by DeForest Kelley, certainly has more screen presence that Dr. Piper from Where No Man Has Gone Before but in The Man Trap his role as an emotional foil to the coldly logical Mr. Spock is yet to be established.
This episode's portrayal of Lieutenant Uhura is particularly interesting in light of Nichelle Nichols's reported dissatisfaction with her role in the original series due to its lack of "significance" and Uhura's (as played by Zoe Saldana) romantic relationship with Mr. Spock in the 2009 reboot of the Star Trek franchise. For one thing, in the first scene in which Uhura is present, she's not at her usual post at the Enterprise's communications console; she's actually at the navigator's station! In this one episode, Uhura demonstrates more breadth in her abilities as a Starfleet officer than she did in the first six Star Trek movies! Uhura then jokes to Mr. Spock about being bored with her duties as the Enterprise's communications officer, and then, if I'm not mistaken, proceeds to shamelessly flirt with the dispassionate Vulcan! Speaking of dispassionate Vulcans, although much less emotional than he was in Where No Man Has Gone Before, Mr. Spock barely seems to be able to control his emotions when he is notified of a crewman's death and then is subsequently confronted by Uhura for what she believes to be (if only she knew!) his cold-blooded reaction (or non-reaction) to the tragic news. The Kirk-Spock-McCoy triumvirate is obviously to take a while to gel into the form that Star Trek: The Original Series fans are familiar with.