First time there is a reference to a rest room (bathroom) on the Enterprise. As Riker and the engineer are talking, she mentions that one of the colleagues is stuck in the restroom due to the aliens taking over the ship. (It's not a restroom but, in Star Trek V: The Final Frontier (1989), Kirk does sit on a retractable toilet, with the warning 'Do not use while in spacedock'. This was released in 1989, after this story.)
The crystalline life form's description for humanoids in the episode spawned the phrase, "ugly bags of mostly water", which has been used as the title of a documentary about Star Trek fans, and as the name of a song by the band Streetnix, as well as being referenced by Dream Warriors in the lyrics of My Definition of a Boombastic Jazz Theme.
In a scene showing the micro-brain in sickbay, there is a sound effect/musical sound taken from Star Trek IV: The Voyage Home (1986). The effect is the same as that used for the alien probe making whale song. Both stories involve problems of communication between humans and aliens.
This episode was the second time on Star Trek for Carolyne Barry. Twenty-one years earlier she appeared as a Metron in Arena (1967) under the name Carole Shelyne.
Critics compared the appearance of inorganic life forms in the story to the plot of The Devil in the Dark (1967).