Trivia: TV's first interracial kiss occurs here. But close examination reveals that Kirk's and Uhura's lips never actually meet. For fear of censorship, the kiss was simulated, so that complaints could be answered with "They only pretended to kiss." Despite this "out," however, the episode was still banned by several stations across the US.
Trivia: When Kirk, Spock, Uhura and Chapel are gathered and costumed to "entertain" the Platonians, Parmen first causes Spock to serenade Uhura and Chapel with a medieval lament in which Spock warns the women to "Be watchful of young men in their velvet prime"; although most viewers and fans didn't understand it at the time (and even today), this line of the song is very much a sexual innuendo. "Velvet prime" refers to the blood-engorged velvet that covers a stag's antlers, allowing the horns to grow to great size. Essentially, Spock's song warned women to be wary of young, horny men.