Writer:	Gene L. Coon
Director:	Marc Daniels
Star:	DeForest Kelley (Dr. Leonard Horatio "Bones" McCoy),  William Shatner (Captain James Tiberius Kirk),  Leonard Nimoy (Mr. Spock)
Recurring Role:	James Doohan (Lt. Cmdr. Montgomery "Scotty" Scott),  Majel Barrett (Nurse Christine Chapel),  Nichelle Nichols (Lt. Nyota Uhura),  George Takei (Lt. Hikaru Sulu),  Walter Koenig (Ensign Pavel Chekov)
Guest Star:	Sheila Leighton (Luma),  James Daris (Morg),  Marj Dusay (Kara)

In the 2007 remastered version of the episode, the ship that Kara arrives in is changed from a 1960s missile/rocket design to a more modern advanced ship that looks nothing like the original. The ice planet also receives a makeover, showing ice and snow in the longer matte shots. (edit) For the first time, the main viewscreen image is rear-projected live during filming in order to allow the actors to interact with the display. Previous viewscreen images were superimposed after the scene had been filmed. (edit) The opening theme music now features a mix of a female soprano and a Theremin. (edit) In this season, the opening credits are in blue instead of gold. (edit) This episode was written by Gene L. Coon under the pseudonym Lee Cronin. (edit)

McCoy: I'll never live this down--this Vulcan telling me how to operate. (edit) Spock: While I might trust the doctor to remove a splinter or lance a boil, I do not believe he has the knowledge to restore a brain.
McCoy: Thank you. (edit) Kirk: Readout, Mr. Chekov.
Chekov: No structures, Captain. No mechanized objects that I can read. No surface consumption, no generation of energy. Atmosphere is perfectly all right, of course. Temperature, a high maximum of 40. Livable.
Kirk: You have a thick skin. (edit) (after McCoy's successful surgery restoring Spock's brain)
Kirk: How do you feel, Spock?
Spock: On the whole Captain, I believe I'm quite fit. It's fascinating! A remarkable example of a retrograde civilization at the peak, advanced beyond any of our capabilities and now operating at this primitive level which you saw. And it all began thousands of years ago when a glacial age reoccurred. You see, this underground complex was developed for the women. Men remained above. And male/female schism took place. A fascinating cultural development of a kind...
McCoy: I knew it was wrong, I shouldn't have done it!
Kirk: What's that?
McCoy: I should have never reconnected his mouth!
Kirk: Well, we took the risk, Doctor. (edit) Kirk: No one may kill a man. Not for any purpose. It cannot be condoned. (edit)

Kara says the knowledge lasts two or three hours, and McCoy says that's just enough time to do the operation. So... how did Kara earlier get the knowledge, go on an open-ended trip hoping to find a suitable brain, do the surgery on the Enterprise, and get back using the knowledge to pilot the ship? (edit) When Kara activates the belt-torture devices, it only affects the landing party even though the Morg slaves are wearing the same belts. She only has three buttons, so how does she get such precise control? (edit) Is Spock really so impressive that Kara stops with him and leaves with his brain? Maybe there's someone else on the next deck with an even better brain. (edit) While performing surgery on Spock, McCoy seems to be standing with his hands at a noticeable distance from where the top of Spock's head is. (edit) An entire scene is devoted to discussing which of three planets to send the landing party to search for Spock's brain. But there are hundreds of people aboard the Enterprise. Kirk could conceivably send a hundred searchers to each planet and still have more than enough personnel for a skeleton crew to run the ship. (edit)

This episode does not have any allusions. Add some now!