As presented in Christmas Waltz, Paul Kinsey’s Star Trek script, “The Negron Complex,” about a world where white people were the slave class, was not very well written. However, it’s worth noting that during it’s original three year run, the producers of Star Trek had actually considered an episode that would have taken place on a planet where light-skinned people were slaves to dark-skinned masters.
According to an interview with DeForest Kelley (Dr. McCoy) in David Gerrold’s The World of Star Trek, one proposed mission would have involved McCoy and Lt. Uhura (Nichelle Nichols) beaming down to a planet where the inhabitants viewed Uhura as a slave-owner and McCoy her slave. Whether the plot was considered too controversial or because the script was not good enough (Kinsey’s perhaps?), no such episode was filmed. A fact which Deforest Kelley regretted because he felt the chemistry between his and Nichelle Nichols’ character in that situation would have been interesting.