I have a fleeting memory of being terrified by the approach of the Doomsday Machine. Assuming it was the original airdate of Oct. 20, 1967, I was just a month shay of being 5 years old.
Fast forward to September 1972. My dad and I had just moved into an apartment complex which was still expanding. As he drove into our "nook", my father spotted two kids roughly my age playing at the edge of a construction pit. Upon entering the apartment, he told me what he saw and suggested I go "make friends".
So, I went and introduced myself as they played with their Tonka trucks in the sand. We talked for a bit and finally, one of the pair, Kyle, asked if I watched Star Trek. I admitted I did not. (At the time, "my" show was "Voyage to the Bottom of the Sea".) He gave me a brief summary of the concept and mentioned he liked to "play" the role of Kirk. As I was a couple of inches taller than Kyle and having "black" Hair (actually a deep, deep brunette), he thought I might serve well as Spock.
So, once I discovered what channel broadcast the reruns and when, I started to watch so I could learn how I should handle this "role" and thus play with Kyle.
So, in effect, I first watched to "win over" a new friend, but eventually it became a passion unto itself.