The following are comments submitted by my readers.

• From Bob Dalley on 2008-02-05 at 1:27am:
  In this episode when Kirk is on the planet, his uniform has no insignia and even when he and his twin beam up there are no insignia on the uniform. A few scenes later, both Kirks have the insignia on their uniforms. Just wanted to point out this error. You may want to add this to your review.
• From Mark J on 2008-03-16 at 10:58pm:
  Shuttles were not introduced to starships until around the 'Galileo Seven' episode, which is rather later in Season 1. There was no fanfare to this effect as far as I know.
  
  Apart from perhaps being a little campy, and Shatner eating the scenery (which I quite enjoyed) and the production mistakes (scratches etc) I thought this was a wonderful episode, especially linking the two halves in with Spock's Vulcan/Human ancestry. OK so the pooch was nothing more than a plot device (where did it come from) but this is more than overwritten by the analysis of a man dealing with loss and the fear that he could lose his crew and himself.
• From TashaFan on 2008-09-09 at 1:10pm:
  I think the lack of insignia on Kirk's shirt is no accident. Since the evil Kirk is supposed to be a mirror image of the good Kirk (I believe the part in his hair is reversed when he first materializes) the insignia on the wrong side of the chest would have made it too obvious that something was wrong to anyone who saw him... I believe this error was deliberate to prevent a bigger problem that would have created a plot hole. The fact that they had to keep reversing the film also accounts for the confusion with the scratches on Kirk's face, most likely. As for not using the shuttle, I remember as a child yelling that at Spock... of course he couldn't hear me. :)
• From 411314 on 2009-06-15 at 1:43am:
  "They could have ruled shuttles out with an easy one liner, such as the atmosphere having a corrosive effect on shuttle hulls..."
  
  Even then, they should have explained why they didn't beam shelter down to Sulu and the other men on the planet to keep them safe untill they could rescue them. I mean, what was the worst that could happen, that the shelter would split into two of itself?
• From Andrew James on 2009-11-18 at 10:34pm:
  I loved the use of camera filters to make the "good" Kirk look beautific.
• From CAlexander on 2011-04-07 at 5:32am:
  I agree, I've always felt the concept here is better than the execution. I've been trying to analyze why. They talk about how it provides fascinating insight on a man's character. What we see is one Kirk with moments of painful indecision, and another Kirk who is decisive but ruled by emotions of lust, hate, and fear. Which I suppose is what they were going for. I think my problem is that I never felt these were two halves of Kirk. I felt that the Good Kirk was the real Kirk. Especially since he is only occasionally indecisive, and it never really hurts him much during the episode, he either gets help from his friends or uses his intellect to overcome it. While the bad Kirk feels like an imposter, not like the real Kirk at all (although he sure is the real Shatner!). We don't really learn anything meaningful about Kirk's character as promised, we see an episode where the crew has to deal with an evil doppelganger of the captain while the captain is suffering from a personal crisis. Which is OK, but not that great. It feels like a few good scenes and a lot of wasted time.
  
  - To 411314: I don't think we know enough about the exact conditions on the planet to complain about how they were keeping warm. They do seem to have beamed down thermal cloaks. Perhaps the crew found it more effective to sit right on the phaser-heated rocks rather than inside the structurally unsound duplicated shelters sent by the ship.
  
• From Mike Meares on 2012-02-17 at 3:49pm:
  "The Enemy Within is story with a high minded idea but poorly executed characterization." - I feel like there is a pattern developing here? lol.
  
  I thoughly enjoy your reviews Kethinov but I sense there is a little "this could have been done better" making it's way into almost every review. I just think this could be said about almost any TV show, especially one made 50 years prior to today.
  
  Despite all the criticisms listed here ( and again they are all valid ) I enjoy this episode very much. I rate it a 5 and I really wish I could rate it higher but the errors are far to glaring to ignore.
  
  I watched this episode again for the 100th time and I still enjoy it. But the techincal errors during the fliming are still a little irritating.
  
  But I beleive the lack of insignia on Kirk's shirt IS, indeed, an accident. When the "other" Kirk first materializes in the transporter room his hair is correctly parted on the left side. The flim was not reversed during this scene nor during the "teaser". So there would have been no need to leave off the insignia.
  
  In fact, the only time I think the flim was reversed was towards the end of the episode when the "kirk's" have their face off on the bridge. The close up of the other "Kirk" was reversed becasue the scratches are on the wrong side of his face. However, I feel this was done by the flim editor who realized that the scene was shot from the wrong angle and corrected it by reversing the flim. ( I guess they were hoping nobody would notice the scratches on the wrong cheek! lol. ) Also in this scene the top part of Kirk's face is cut from view so you really can't tell the part in his hair. It is still a mystery to me as to why the flim editor felt the need to reverse the film. They wanted the other "Kirk" looking left to right instead of right to left. But why is still a mystery?
  
  And the reason I think the lack of insignia was a big mistake was the fact that during the "teaser" neither Kirk had an insignia and during the first scene after that in the transporter room with crewman Wilson the other "Kirk" had no insignia. But the very next scene of Scotty escorting a dazed Kirk to his cabin there is an insignia on his shirt! In fact, from that moment on both "Kirks" have their insignias.
  
  The flim editing was extremely poor in this episode! I could name several scenes that are clearly out of place and moved around. If you are going to move scenes around at least make it look normal.
  
  Despite this though there are a few things I like about this episode. And, again, for me it is the develpoment of the secondary characters. I like the idea of two men manning the transporter. Wilson is a good character, as well as Fisher and Farrow as well. But just like Riley, they were on a couple of episodes and then gone. Too bad.
  
  Also several scenes stand out for me. When Spock tells Kirk he doesn't have the right to be vernable in the eyes of the crew that was very powerful. And again towards the end of the episode Spock explains "being spilt into two halves is no theory" for him. Great scene.
  
  And I resist calling the other "Kirk" evil because I don't think that is correct. Like Dr. McCoy said in the episode that the other "Kirk" isn't "really evil, he's human!" That whole explanation during that scene by the doctor is so great. McCoy was right. Both "Kirks" were the real Kirk.
  
  I don't feel the episode is a waste. But it definitely has it's problems. I do feel that with some rewriting and better flim editing this could have been an outstanding Star Trek episode.
  
  A small nitpick of mine. When Spock says "Thermal Heaters were transporter down, they duplicated. They won't operate." I have to ask myself, If I duplicate a piece of equipment why won't it work? The Transporter Malfunction seemed to be duplicating everything and separting their emotions. Eh........Manchines don't have emotions..... Hello!
  
  
  
  
• From Kethinov on 2012-02-18 at 9:08am:
  Of course "this could have been done better" makes its way into almost every review. Otherwise every episode would get a 10! :)
  
  For most episodes it's the reason for and degree to which it could have been better that's interesting to analyze. Anything else would just be shameless gushing or bashing.
  
  Since most people come here to find which episodes were the best (or worst) of Star Trek, I try to write carefully balanced reviews and highlight both the good and the bad in each episode.
  
  The rating will thus generally be weighted against the "what worked" and "what could have been better" analyses. The pattern is quite deliberate.
• From Ken on 2012-07-25 at 12:09pm:
  I believe Mike Meares has it correct. The scratches on the other side of the face, were a result of shooting bad Kirk's scene from the wrong angle. I believe they realized that his character would not have been speaking in the correct direction, so they had to reverse the image to make it seem so. However, putting the scratches on the other side of the face was even more noticable.
• From warpfactor 10.1 on 2012-08-08 at 10:19pm:
  One of the many splendid things about this episode is the animal that is presumably from the surface of the planet. Not only is it able to stand temperatures of - 120 at night but, remarkably, it also looks a bit like an earth dog onto which someone has stuck a horn and antennas.
  A little known piece of trivia is that when Margaret Thatcher was looking to use a Star Trek episode title as a catch phrase to demonise the trade unions she had decided on 'The devil in the dark' before Sir Geoffrey Howe, an avid Star Trek fan, convinced the rest of the cabinet that they should use 'The enemy within' instead. She never forgave him.
• From Glenn239 on 2012-11-06 at 4:44pm:
  ‘5’
  
  Sulu: We’re freezing to death down here captain. Can you send us a shuttle?
  
  Kirk: No, don’t be absurd. We can’t do that. We don’t want to break up our set. You don’t want us to have to start collecting all over again, do you?
  
  Sulu: No, but what about the hot coffee we were mentioning in the previous scene?
  
  Kirk: Are you mad? Too risky. What if you drink the angry coffee by accident?
  
  Sulu: Ok. Can you beam down a shelter?
  Blankets? How about a fireplace with a warm fire already burning in it? How about just heating stuff up from around the ship and beaming it down? Can you at least phaser out a hole in the ground so that we can get out of the wind?
  
  Kirk: No, no, no, no and no. Stop whining and be the dramatic tension of the episode like you’re trained to be. Oh – and those phasers you used to warm the rocks around you three scenes ago? Nice try mister. We’re beaming those up so that you can’t do that again.
  
  Sulu: Captain, this episode has a lot of holes in it.
  
  Kirk: I know. The most interesting premise was when evil Kirk was going to abandon you, but we even screwed that up by making sure that the whole crew knew it was the wrong Kirk. We’ll try again later this season. Next time we’ll explain the shuttle thing by having it be a shuttle accident. Instead of two of me, we’ll have some dickish Commodore. It’ll be great. Kirk out.
  
  Later that day…
  
  Kirk: So you see, Yeoman Rand, it wasn’t really me, it was just the evil part of me.
  
  Rand: Oh, yeah. Merely the half of you that wants to rape me. Nothing to worry about there.
  
  Kirk: Yes, that seething cauldron of raw aggression is safely back where it belongs – inside me, frothing just below the surface, and held in check only by the will of that super wimpy guy you saw who couldn’t decide his way out of a paper bag.
  
  Rand: Perfect.
  
  Kirk: Really?
  
  Rand: Yes, captain, you see I’m a women. I crave long-winded overly-rational explanations for all my relationship difficulties, and I do not hold grudges for past slights far into the future. I’m sure that you being slapped back together in some untested half-assed transporter experiment has worked perfectly well, and there’s no possible way that you’d have nodded your head to Spock indicating you were properly balanced if you were not. Nothing could possibly have gone wrong there.
  
  Kirk: Wow, this show really is out in space, isn’t it?
  
  Rand: Yes, and I look forward to being part of the adventures for many more seasons to come.
  
  Kirk: I’m sure you do.
  
• From Schreck on 2013-05-23 at 6:31pm:
  Our first transporter accident episode sees kirk split into two halves, the uninhibited and the meek…although this episode has a good premise the execution is poor…Shatner’s acting is good, but even that can’t save this episode…I give it a 6.25 and my brother has it as his third lowest of the original series coming in at a 5.5
• From Trekkie on 2013-06-21 at 4:43pm:
  This episode, in my opinion, was one of the better episodes. I liked how they showed both Kirk's evil and good side, and also how the episode states that we need to have a little of both (good and evil, that is) in order to make beneficial desicions and be stable.
• From Katie on 2013-07-07 at 6:24pm:
  Aside from all the other plot contrivances, why was it so hard to find "evil Kirk"? Why didn't "good Kirk" just stay on the bridge and announce that any "Kirk" not on the bridge was the imposter?
  
  I mean really.
• From 10toes on 2015-08-09 at 11:46pm:
  Actually, only the last pill was placebo. The ones before that were the real deal.
  Still, doesn't explain why that last pill changed her appearance...