Maybe I just haven't seen enough of Lost in Space to understand the motivations. It seems like Dr. Smith was always trying to kill off the rest of the characters, or sell them out to hostile aliens. Why did they take him along? Why didn't they just put him out the airlock?

I understand the writers need the antagonism to create tension as a plot device, but it just seems too hard to believe anyone would put up with a guy like that. There must be some in-show rationale for keeping him that I missed. So what would that rationale be?

  • 6
    As opposed to murdering him in cold blood or abandoning him on a lifeless planet, you mean?
    – Valorum
    Commented Jun 1, 2014 at 16:17
  • He is a doctor. Chances are he'd be useful at some point. And, as others have mentioned, their only alternative would be to kill him, which the moral Robinsons are loathe to do, even to Dr. Smith. Commented Aug 15, 2016 at 1:25
  • You have a limited crew, isolated, in the vast reaches of space. Everyone there has vital skills needed for survival. I'm guessing you don't what to ditch your medical professional. Side note - When I was a kid we used to role-play Star Trek in my family. My siblings would torture my younger brother by our own version of the Kobayashi Maru (before the concept ever came up, pre-movies) - aliens won't destroy the ship if we jettison Scotty from the service passages into space. It would end with my little brother either distraught from being cursed by a dying Scotty, or death by aliens. Commented Aug 26, 2016 at 16:37

7 Answers 7


It's not an in-universe answer, but there's some interesting background here. The original pilot did not include Doctor Smith or the Robot. This included the sequences that were later used in early episodes where they took the trip in the chariot to a warmer climate. In order to use that footage, they had to come up with a reason Doctor Smith and the Robot did not go with them on that trip.

When Doctor Smith was added, the original intent was for him to be in the first few episodes as a saboteur and bad guy, but that they'd kill him off or he'd end up left behind or something like that. That's why he was originally credited as "Special Guest Star." This was also when Lost in Space was airing opposite the 1960s version of Batman from January of the 1st season of Lost in Space onward.

The tone for the 1st season of Lost in Space was black and white and started with a more serious and darker tone. Batman was in vivid color. To combat that, Irwin Allen, the producer, guided the show to a more and more campy and humorous tone. (And went to color, with an emphasis on bright colors in the 2nd season.)

Jonathan Harris was still, during the first season, not in a secure job, since his character was supposed to be written off the show, but Harris, of course, wanted to stay, so he worked hard at every chance to change his character from a dark heavy to a comical and likable trouble maker. (This included coming with, on his own, all the names he called the Robot, like "bubble headed booby.")

This fit in well with Irwin Allen's plans to make the show funny (and by that time Star Trek had the serious science fiction audience) and to fight Batman with more of the same. One day Allen burst onto the set, pointed at Jonathan Harris and said, "YOU!" Everyone looked at Allen and Smith and Allen said, accusingly, "I know what you're doing!" then said, "I want more of it!"

For an in-universe answer, while Don West would have gladly gotten rid of Smith, at least at first, even if he was evil (as he played it at first), the head of the expedition was John Robinson and he would be directly, on a personal level, responsible to his wife and children, and if he killed Smith, or let him die, or marooned him somewhere, that would have turned him into a murder in the eyes of his family. Maureen, on the other hand, repeatedly demonstrated a high level of compassion for Smith and actual enemies. This was the 1960s, and the image of a woman as gentle and compassionate, especially in a mother, was expected.

  • 5
    Large portions of this answer are flat-out incorrect. Smith was never intended to be killed off after a couple of episodes. That rumour seems to stem from a joke told in a cast interview : scifi.stackexchange.com/questions/8192/…
    – Valorum
    Commented Dec 28, 2014 at 9:29

They basically had two choices: keep him around, or kill him. (The latter includes abandoning him on some planet.) The ship wasn't big enough to have a brig, and there weren't enough people on board to act as guards.

I remember (not very clearly) an early episode in which Dr. Smith was adrift outside the ship in a space suit. They can rescue him, but if they do they'll go off course and never get back to Earth. Don West asks why they shouldn't just abandon him; Maureen Robinson (June Lockhart) replies, quite vehemently, "Because he's a human being".

That set the pattern for the rest of the series. They didn't kill him because they're not killers.

  • Well they might have left him somewhere, rather than actually stuff him out the airlock. But I guess I see it now. Kind of a 'no human left behind' kind of thing.
    – JustJeff
    Commented Oct 30, 2011 at 2:18
  • In that episode, there was no place they could leave him alive. Once they had gotten themselves lost to rescue him, abandoning him would have been -- shall we say -- rather awkward. (And of course the real reason was that they wanted the character in the show.) Commented Oct 30, 2011 at 2:32

Apparently no one here has ever owned a house cat. It pretty much does nothing but ignore what it has been told not to do, eats free meals, constantly takes naps, will maliciously bite and scratch any human in the house for imagined or perceived slights (might kill you on a whim if it could), runs at the slightest hint of danger, demands attention and affection when it wants it, demands anything when it wants it, has occasional bouts of manic activity, is persnickety about its appearance and demeanor especially when it thinks it is being watched, continually acts as if it could care less about the humans around it - but if left alone will bemoan the fact that it has been abandoned. When least expected, behaves momentarily bravely, lovingly, and in the interest of others. Invariably it is most loved by the children in the house hold, and put up with or ignored most of the time by the adults, who either seldomly take it seriously, or may even detest it.

Dr. Smith is the Robinson Family cat.

  • 1
    Jeez. You really don't like cats, do you?
    – JRE
    Commented Sep 23, 2015 at 6:51
  • 1
    Wow, it's like we're soul brothers. Upvoted just for making me laugh. Commented Jan 30, 2018 at 3:24

All of the answers above are very true: they weren't villains, he was a human, they were kind, he was extremely good at talking he way out of things, etc. However, there is another little thing that might have also factored in-universe.

At the beginning of the show, Zachary Smith fills the role of-besides being the actually competent saboteur-of their medical doctor, and clears the family's health for the journey. While this was largely forgotten as the series progressed, he still held a medical doctorate. In the event that one of them was sick, injured, maimed, mauled, etc, having a medical doctor there to treat them would be a blessing.

Granted, his medical degree is virtually never mentioned again, but he still holds it.

My theory on the subject...

  • I was always under the notion that his medical degree was an exaggeration. In addition to his other deplorable qualities, he was also a fraud.
    – SMBiggs
    Commented Dec 20, 2017 at 7:38

I guess I came from a very close knit family because even at 6 years old, I could never understand why they put up with Dr. Smith. I'm quite a bit older now and I still can't. Frankly (as a kid) I only watched Lost is Space if nothing else was on. I think as quickly as the 2nd or 3rd episode, Dr. Smith is demonstrating his "voting power" by having the robot crush a helmet, implying he will have the robot crush their heads if Maureen & Major West don't abandon John who crash landed on a planet and head back for earth.

I agree with others who say the Robinsons were decent people and couldn't have just killed him off, but the idea that any parent, especially a father would tolerate Dr. Smith endangering his family week after week was totally absurd. Outer space travel was very fresh in the 1960s and should have had enough challenges that a Dr. Smith character within the group was not necessary as a plot device. I thought Star Trek was far superior to Lost in Space even at 6 years old and still do!


There is the fact that he was a good talker, and very good at shmoozing his way back into the group. He takes advantage of the good nature of the other characters, knowing that they would struggle to actually kill him.

And yes, it becomes inplausible, but over a short period, he is just like the person at work who is a waste of space, but somehow manages to keep their job.


Dr. Smith was the character everybody loved and hated at the same time. Whenever he did something diabolical he was saved or allowed to return to the Jupiter II. Will was the smart child, Penny was the cute little girl, Judy was the beautiful young woman, Maj West the dashing young man, Maureen was the wife, mother, friend with common sense and appeal and John Robinson was the leader, father and savior of the group. Best of all was Robot..the B-9 Robot...everybody loves robots! So with all these characters there had to be one character that would upset the apple cart, so to speak. While the children would get into "trouble" doing what kids do, Judy was the "love interest" of Maj West and Maureen would be making sure that things ran as smoothly as possible, Maj West and John had to be the brains and muscle of the group and handle all the major problems that appeared each week. With all those characters being "nice" there had to be someone who was just plain bad, and bad at being that as well...so there you have Dr. Smith. Dr. Smith was the cause of the failure of the Jupiter II to complete its mission. He was responsible for almost killing everyone on board. He programmed the robot to sabotage the mission and failed. That set the stage for the whole series. Dr. Smith would be expected to cause problems and be very comical at that as well. Thats how all Lost In Space fans fondly remember him.

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