Charlie X was TZ's It's a Good life ten years later. Matheson wrote for both series anyway.
True, although Matheson only wrote a single Star Trek episode, "The Enemy Within," ....
Ya write that episode, your worth as a Trek writer is secured. One of the best pieces of TV ever, imho.
2. As to the OP: the Man Trap, because of its music; story-wise, it's more Outer Limits, with a misunderstood monster