Network executives ordered director David Alexander to shoot a take where Kirk and Uhura did not kiss, just so it would be available. However, William Shatner crossed his eyes at the camera, making the take useless.
Nichelle Nichols said this was her favorite episode, due to Uhura's being allowed to do something plot-crucial as opposed to her usual role as a glorified receptionist.
Nichelle Nichols has said that the Star Trek production offices received more mail on this episode than any other episode in the history of the series and, surprisingly, none of it was negative.
There is some dispute about whether the kiss actually occurred. According to the on-screen footage, it appears that the actors' lips touched. However, both William Shatner and Nichelle Nichols claimed in 'Star Trek Memories' that NBC exerted pressure to forbid lip contact and to use a clever camera technique to conceal the "separation". Looking closely, it appears that the actors' lips are not touching; the angle only makes it look like they might be slightly touching.