1. The original pilot, “The Cage,” was partly killed for being too sexy
Why did NBC choose not to air the first Star Trek pilot, starring Jeffrey Hunter as Captain Christopher Pike? People usually blame it on a too-cerebral script, with too much deep philosophizing and introspection. But in fact, a major reason had to do with NBC’s Broadcast Standards Office, being concerned about the “eroticism” of the pilot, with the green dancing girls and the kissing and all that raw sexuality. (To be sure, the network was also worried that it was “too smart,” a female first officer was going too far, and Mr. Spock looked too demonic.) Later, after Trek was on the air, the producers used the network’s concerns about sexuality to their advantage — they would deliberately put sexy stuff into episodes for the network to freak out about, so the censors wouldn’t notice other things. For example, in the episode “A Private Little War,” the producers deliberately put in a scene of Kirk having an open-mouth kiss with a half-naked woman, so the network could throw a fit about that — and not notice the blatant Vietnam allegory.
Source: Inside Star Trek by Herb Solow and Robert Justman, pp. 60 and 356.