The Robinson family banish Dr. Smith from the Jupiter 2. He takes refuge in an abandoned spaceship where he finds a machine that can materialize anything. In an attempt to get back on the Robinsons good side he gives them the machine which plays on the family's greed.

Lost in Space's only Christmas program. Will uses an alien transporter to send himself back to earth. However, many people believe the Robinson family to be dead after hearing the ship went off course. Nobody on Earth believes him, and they lock him up with the intention of sending him to a boys' home. Will escapes the family home he's in, and wanders around these clueless bunch of townspeople, but finds carbon tetrachoride — needed for the food processors on the Jupiter. Eventually he convinces another boy, Davey, to let him out, and let him return to the planet he came from. He returns to Priplanus with this bottle. Of course no one believes his adventures until he produces the bottle, plainly labeled as coming from Earth.

While the rest of the men are away, Dr Smith and the Robinson women are affronted by a mysetrious man in gold, who claims to be at war with a race of green aliens. Penny meets the green alien, and takes a liking to him, and immediately hates the Golden Man. When they are faced with the reality that their planet may be blown up due to war, Penny risks her life to save her green friend, while Dr Smith makes other startling revelations, and renders the family helpless.

While playing a outdoor match, Will and Smith's ball explodes, and as the smoke clears there ball has turns into gold. the ball rolls into the cave which has 3 aliens inside, the alien wants the robot , which is later stolen when Will refuses to let them have it and Smith does. Can the crew get there robot back.

John Robinson is possessed by an alien spirit. The alien forces the family to prepare to return to the spirit's home world, even if it requires he sacrifice Will to keep his secret from the rest of the family.

Will and Dr. Smith stumble upon another robot. More capable than their own robot the alien robot works to gain the confidence of the Robinsons. At a critical point he plans to transport them to his home planet as slaves.

An alien boy is sent to Priplanis to validate his prince status. Will is drawn into a battle to the death unbeknowest to his father. Once his real intentions are known John substitutes himself in the challenge and the Alien Ruler substitutes himself for his son.

Dr. Smith holds a seance to contact his Uncle Thaddeus. Instead a spirit creature is contacted and creates havoc for the Robinsons. It is later discovered that the ""spirit creature"" is a physical creature, rendered invisible by the properties of the ""ionized gas"" in the bog from which it came.

When a troope of Galactic Gladiators arrive on the planet, they challenge Professor Robinson to a duel, which will be aired all of the galaxy. John declines saying he isn't interested in physical combat. Dr Smith takes up the offer when he makes a deal that if he wins, he will be returned to Earth. Unbeknownst to him, if he loses, which is a near-certanty, Earth will be destroyed.

When Dr Smith's cousin Jeremiah Smith arrives on the planet, everyone welcomes him, except Dr Smith. Dr Smith alienates himself from the family, and refuses to return until his cousin leaves. It is later discovered that Jeremiah's reaosns for being on the planet are far deadlier than anyone imagined.

Penny "imagines" a new companion, which is a disembodied life force living below the surface. Dr. Smith accidentally injures Penny, leading to the creature taking his anger out on the entire planet.

Luminous aliens capture Dr. Smith and plan to replace their burnt out computer with his brain. Smith bargains with them and they attempt to use Will's brain instead.

The Robot suddenly announces that the Jupiter II is approaching Alpha Centauri. Everyone is suprised, and the ship lands on a planet, where they are greeted by a group of people who appear to be teenagers from Earth. It turns out that they are aliens who live like Earth-style hippies, and they are incapable of growing old. They want to age normally, and to do this they want to get the older members of the Robinson party to leave in the Jupiter II while the younger members can stay behind and be used in an experiment that will make it possible for them to do so. The aliens trick the older members of the Robinson party into leaving, but Will pulls a fast one on the aliens and the Jupiter II eventually returns to the planet, and Penny, Will, and Dr. Smith, who somehow passed himself off as a young person, are rescued.

A strange blue fog seems to be engulfing the Jupiter 2 periodically. Dr Smith and Will commment seperately that they want to be left alone. When the members of the Jupiter 2 begin to randomly disappear as the fog comes, Dr Smith thinks he is to blame. Eventually Will discovers a strange creature which takes over Dr Smith. The creature tells Will that he is his own Id. Will finds out his Id is a creature he created full of Will's own personal demons, thoughts, feelings and insecurities. Will defeats the creature by overcoming his ""fears"" and throws the powerless creature in the power core. The members of his family are returned.

Will and Dr Smith discover an old, abandoned Android Machine. When Dr Smith plays with the buttons on the machine, he accidently orders an Android. He thinks he has it for free, and uses her as his personal slave, assuming she has no human emotions. What will he do when the owner, Zumdish, and his guard turn up...demanding payment?

The Keeper, played by Michael Rennie, is a zoo keeper. He wants to take the children and add them to his collection. This episode is the only two-parter from the series.

Dr. Smith, Will, and the Robot are accidentally launched in the Space Pod. They land on a planet that is controlled by an alien machine that creates illusions to confuse visitors and drive them away. The Jupiter II lands and rescues them, and the robot destroys the alien machine.

The Space Pod lands on a planet that is inhabited by creatures who all look alike, and aspire to be different. They capture the Robinsons and make duplicates of them with the objective of using the duplicates to fly the Jupiter II back to Earth. Will is not duplicated, and he thwarts their plan.

Dr. Smith disposes of a plant that has grown out of control, but once outside the plant attaches itself to the Jupiter 2. The plant apparently believe that Dr. Smith is its mother, meanwhile the ship is attached by a brave space warrior.

The Robinson's come across a group of space hippies who are trying to destroy the planet the Robinson's currently inhabit. Up up to the Robinson's and Dr. Smith to stop them or they will all be doomed.

The Robinsons can not understand the language of a visiting family also on the planet. The aliens are called Taurons, and come to use the planet as a new colony. However Dr. Smith causes problems between the two camps when he panics and draws a gun on the new family. The Taurons end up not liking the planet and want to be alone, so they leave.

Dr. Smith eats some alien fruit which transforms him into a giant. Convinced it was the Robinsons trying to kill him, he plots to take them out.

The Jupiter 2 is pulled into a giant alien spaceship where there are advanced bubble-like creatures. While John and Don look for maps and equipment Dr Smith and Will look for trouble.

Dr Smith and Will befriend an old miner named Nerim. After a series of earthquakes indicates that the planet is breaking up, Dr Smith tries to convince them that it is merely the effects of mining, and no harm will come to the planet. John informs him that he is wrong and that the Robinson family will be departing within the day. It is a race against time to escape the crumbling planet.

Penny and Judy stumble upon a mirror. They discover someone is on the otherside. Before they know it they are transported to the mirror universe which is occupied by only one person, a boy who is lonesome for companionship.

The crew are outside playing ball when a magician called Zalto. Dr. Smith uses Zalto to conjure up a space ship so he can use it to get back to earth.

Dr. Smith's finds an alien ship and wants to use it to get back to earth, but he doesn't count for the owner of the ship admiral zahik to turn up and wreck his plans.

A storm looms up and the two gloves of Thor appear from space and straight into the waiting hands of Dr. Smith. Then are then taken away to see the real Thor who will decide there fate.

The Robinsons take in a Princess who is fleeing from a bounty hunter. Will is captured by the bounty hunter, who wants to trade the boy for the princess. the robot then comes up with a idea to save the day.

The Robinson's communications system is knowcked out, and they discover that the culprit is a female warrior, who is planing on making this planet a colony for her people. She encaptures the members of the Robinson camp, and puts the men to work clearing a landing platform and erecting an arc. Meanwhile she keeps the females seperate and teaches them of the virtues of females, and the vices of males. Dr Smith becomes her escort to get out of work. Just before her colonists arrive, John, Will, Don and Dr Smith destroy the arc, and the colonists leave. It ends with Noble Neolani questioningthe value of men, and perhaps they weren't as bad or stupid as she thought.

Dr Smith discovers another Android Machine, in the middle of a dangerous fisher. When he tries to order something, he is trapped inside the machine. Later when Will tries to get him out, he too is sucked in. Zumdish arrives on the planet in order to destroy the faulty, forgotten machine. Meanwhile Will and Dr Smith discover the magical Toymaker's world, as they are mistekn for toys. They later discover they are close to earth. Will they return to Earth, be blown up, or Will Professor Robinson and the Robot be able to save them.

Will returns to camp following a cosmic storm. John and Maureen are not there as they are at the weather relay station for a few nights. When he gets there, the rest of the family are acting strange. He finds out they are androids, sent to learn how to cope like the Robinsons and teach the rest of their race when they return home. The real Robinsons, are kept in a tube, as they are not allowed to come in to contact with thier double. Will must teach them to become like their counterparts.

Will and Dr Smith are confronted by a knight, who says he is on a quest to seek out and destroy the beast Gundemar. Penny, meanwhile, meets Gundemar and befriends her. Will becomes the pageboy of the knight. When it is discovered that the beast is woman, the knight is unsure whether he can still kill it, leading him to question his life's future.

Penny meets up with Verda the Android Dr Smith ordered, who is on the run from a super android, IDAK. She is now much more human-like. IDAK however is faulty and is incapable of crushing anything or anyone. Another OMEGA-IDAK is released, and vows to ""crush, kill, destroy."" Verda hides with the Robinsons but out of fear she and Panny run, when Zumdish and his guard arrive to get her. IDAK is defeated, and Verda and the faulty IDAK take off together, obviously in love.

Dr. Smith answers a distress call from an alien space ship. He arrives there using the Space Pod, and discovers that the aliens want him to operate on (actually, repair), their leader. It turns out that the aliens are a race of some sort of robot that survive as long as their leader, who functions as their central control timepiece, is in working order. The Robinsons come to Smith's rescue in the Jupiter II. The leader is repaired by the robot, and the extended space family Robinson leave the alien space ship safely.

Professor Robinson is caught in a matter transfer emission ray, and subsequently ends up in another dimension where he is confronted by a version of himself and Don. However this realm is the opposite of his own dimension, the anti-matter world, where everything in reality is twisted. The evil John returns to the family and attempts to take over the Robinsons and take over John's life. Will he get away with it, or are Will and the Robot able to defeat him, and restore the world to it's natural order.

As they are rehearsing a play, Dr Smith, Will, Penny and the Robot encounter a creature who appears to be suffocating. Dr Smith refuses to help out of fear but Penny helps him. The alien puts himself in human form so that he may breathe the atmosphere. He says he is Mr Arcon. Penny takes him back to the Jupiter II to rest. Later he gives Penny a gift which he says she must guard with her life. He tells her that as long as she wears the belt, she will be safe. He disappears, and it is not long before a group of aliens turn up, looking for the belt. They inflict immense cold on the planet as a way of trying to get the belt, but Penny refuses despite pleas from Dr Smith. Dr Smith makes a copy of the Belt and tries to give the fake to Aliens. They are angry, but still want his help. They promise to return him to Earth should he get the belt. Dr Smith and Penny go through the Alien's machine, where they have created a world from the Dr Smith's memory, which will trick them in to

Before leaving their planet, the Robinsons meet a boy alien called J-5. They take him with them to return him to his home planet. They meet a strange ship, which turns out to be an earth ""lighthouse"" for lost ships. Thinking this ship will help them with extra fuel and star charts they celebrate, however when J-5 learns that they don't have enough fuel to take him home, he angrily sets about to destroy them all with a creation of his imagination. J-5 begins a new life at the lighthouse, and the Robinson's leave in the knowledge he will be looked after by the kindly, old lighthousekeeper.

A crew led by Captain Kraspo is searching for the missing Princess Alpha. They bring Will aboard their ship who makes them think the Penny might be there princess, because of this the train Penny to be the future ruler of there planet.

Dr. Smith and the Robot are exploring a cave. Smith pushes several buttons on a conspicuous control panel. The buttons activate a cyborg creating device. It up to Will to stop Dr. Smith.

A caveboy appears and attempts to lure Penny away, but she refuses, and is instead caught in a net. She is transported to an intergalactic zoo, were she will be puton show, meanwhile Dr. Smith tries to take over the zoo.

When an alien believes that the Jupiter 2 has fired a missile at them that alien puts the crew in grave danger for there lives.

Dr Smith is confronted by an identical look-alike called Zeno, who is on the run from the law. Zeno makes him trade places and Dr Smith, out of fear confesses to Zeno's crimes. He is arrested and he and Will taken away to appear in court. Will the real Zeno be caught before Dr Smith is boiled in oil?

The Intergalactic Delivery Service comes to Priplanus. Once again Dr. Smith seeks transportation and has Will "test drive" the spaceship. Will returns much smarter than when he left. Smith realizing the same could happen to him, the increase of intellect, boards the spaceship. His trip, however, ends in his rapid aging and subsequent impending death. To make matters worse, the owner of the spaceship has returned to take the vehicle back, stranding Will and Dr. Smith in their altered state.

The Jupiter 2 lands on a planet which serves as a junkyard. The Robinson's food supply is dwindling. So Dr. Smith tries to sell the robot and the ship in order to get food. Can Dr.Smith be stopped?

Alonzo P. Tucker returns, this time more in keeping with the pirate character he tried to create in his first appearance. This time Tucker is searching for Billy Bones' treasure, and is using the head of Billy Bones, which is kept in a box, to help him find it. He has three cutthroats with him, and he has to find the treasure and keep the cutthroats from endangering the Robinsons. Tucker's robotic bird is back again, and continues to torment the robot.

Dr Smith and Will become trapped in a cave during a cosmic storm. Will is accidently pulled through a cosmic time warp, and ends up on Earth, in Scottish castle. He meets a headless ghost called Hamish who was beheaded at the Castle. Hamish is trapped there due to the callous crimes he has committed. They rest of the family manage to get Will out, but Hamish follows him. They decide to re-create the time warp, and send Hamish home, and with him Dr Smith, carrying star-charts and maps so that he may send a rescue mission to save the Robinsons. Upon re-entering the warp, Dr Smith drops the charts, and Will runs after him to give them to him. They are both taken. When they reach the castle again, Dr Smith and Will realise that they are not in their time. Also, Hamish becomes angry when he realises that Dr Smith is a liar, and has no intention of helping the Robinsons. As an act of reveng he sets out to destroy Dr Smith. In the end, Will and Dr Smith return to the planet, and Ha

Poor Don West is sent to a prison camp.....WITH Dr. Smith! Don and Dr Smith are installing some equiptment, when Dr Smith comes across and alien prison escapee. The priosoner alien makes Dr Smith change jackets and then runs away. When the prison guards catch up with Dr Smith and Don, they arrest them for aiding an escape of a prisoner.

Jimmy Hapgood lands on the planet and the Robinsons befriend him. After helping him fix his spaceship the Robinsons try to convince him to take Will and Penny back to Earth with him. Dr. Smith tries to get aboard the ship instead and take their place.

With the power source of the Robinson's at a low, they are unable to recharge the Robot. As a result of this the Robot leaves the group, not wanting to be a further burden to them. When they later change thier minds, they cannot find the Robot. Will and Dr Smith discover late one night, but due to the gases in the area he has grown to be bigger than a house. Will decides to only way to reverse the process is for them to go inside him, and work it internally. Will they get out in time?