Tim is placed on the Teacher of the Year selection committee.

In a department store, Martin is frozen into a mannequinlike pose.

Reporter Tim O'Hara, while covering a flight of the Air Force X-15, finds a spaceship that contains a genuine martian. The martian is a professor who specializes in the planet Earth and now has to repair his spaceship before he can go home.

Martin's latest machine effects a mind swap with Mrs. Brown.

Martin reads about a $2 billion American space program, a program he knows is doomed for failure. Not wanting to see the American government waste $2 billion, Tim writes himself a fake letter to the newspaper which includes Martin's nighttime musings; Tim thinks Martin's mumblings are key to the flaw in the space program. Based on the fake letter, Tim writes a newspaper story criticizing the wasted $2 billion. Tim's masquerade is uncovered by the government, agents for whom think he's a spy working for the Russians. Tim is questioned under a lie detector, and he fails miserably when it comes to questions about Martin. So the agents call in Martin, the agents who question him under the lie detector, under hypnosis, and through brainwashing. Martin overcomes each, to him, primitive method. But he can't overcome the truth serum, and he spills the beans about being a Martian. It isn't until then that the agents let Tim and Martin go. They figure that Martin is crazy and delusional, which is causing stress on Tim which in turn made him write the letter.

The O'Hara's have new neighbors, the Richmonds, within the family being young Stevie and his grown up sister Jennifer. The foursome go on a picnic to Sunset Mountain, since Martin needs to pick up some bling, an alloy located there but that has not yet been discovered by humans. Stevie has a vivid imagination and likes to pretend he's from Mars, which intrigues Martin. That's OK with Tim, as that means he can spend time with Jennifer alone. However Jennifer is concerned with Stevie's ability to discern reality from fantasy. While Martin goes off to collect his bling, Stevie plays a game of pretend and climbs up the mountain, but reality hits when he can't get down on his own. Martin suggests that Tim climb up and get Stevie as an act of heroism, but Tim is afraid of heights. Martin reassures Tim that he will be safe with the assistance of his remote control gravitation machine. Tim bounds up the mountain, but doesn't know that Martin's machine breaks while he's half way up. Tim and Stevie have a couple of close calls, which Tim thinks is Martin just trying to be dramatic. Although Tim faints when he finds out the truth about the gravitation machine, he shows that one just needs to have a little faith to accomplish mountains.

Tim diverts Mrs. Brown's attention while Martin returns the spaceship to the garage.

A short circuit in Martin's transmitter puts him and Tim on nationwide TV.

Martin allows himself to experience an emotion foreign to Martians: love at first sight. He falls hard for Peaches Ancream (Kathie Brown), that being her real given name since her father had a sense of humor. It is also an appropriate name as she is an exotic dancer. Peaches and Martin hit it off, so much so that Martin wants to marry her after their first date. Peaches admires honesty more than anything else in life, the reason that she broke up with her last boyfriend, Police Officer Thorp, who is still harboring strong feelings for Peaches. Martin decides to tell Peaches the truth about himself, which Peaches doesn't believe. When Officer Thorp confesses about the reason for his lies - he told her 6 different places where he was from since in reality he is an orphan who doesn't know - Peaches goes back to the man she feels is being more truthful.

Tim talks Martin into temporarily giving him a Martian power. Martin decides to give him the power of levitation for a 24 hour period. When he thinks the power practically useless beyond performing mere parlor tricks, Tim asks for another, to him, more useful power: mind-reading. Martin grants him his wish, to be activated the next day and to last until midnight. Tim also uses this power for parlor tricks, which gets him into trouble. But he also wants to use it for an interview he has that afternoon with Councilman Jack Gramby. Tim wants to write a story about the Councilman's true political intentions. Tim is unable to read his mind because the Councilman is uncommitted in his political intentions, even to himself. So Tim writes a story on what he calls the mental ping-pong of the Councilman. The Councilman telephones Mr. Burns, Mr. Burns thinking that it is to sue the paper for libel. Distraught about probably losing his job, Tim goes into hiding for the rest of the day. However when Mr. Burns finds Tim just before midnight, he tells Tim that Gramby actually wanted to congratulate the paper. Reading the story made Gramby realize that he as a politician really did need to take a stand. Mr. Burns wants Tim to do such an exposé with all politicians at City Hall. Unfortunately Tim's mind-reading powers are just about to run out.

Martin wants to help Tim with the household expenses, and without a money earning activity, decides to sell art he's currently painting to relive boredom. Martin can paint in the style of any famous artist. Mr. Green of the Green Gallery notices Martin's first piece is just like a Van Gogh, and eagerly takes and sells it. As such, Mr. Green commissions Martin to paint some more and they sell as quickly as Martin gets them to the gallery. Mr. Green wants to have a showing of Martin's work. When Tim mentions that this might not be a good idea as it may raise questions about Martin himself, Martin offers Tim up as the true artist of the paintings. At the show, Mr. Bentley, the art expert brought in the evaluate the show, is skeptical that Tim painted all the paintings, since they are all in different styles. Mr. Green suggests that Tim provide a real life demonstration of his painting process. Martin assures Tim that with his help, he can indeed paint. However, when Tim's demonstration is supposed to start, Martin has an allergic reaction which is affecting his Tim-assisting painting finger. Martin has to find out what he's allergic to and get rid of the item. Tim is nervously on his own until Martin finds the allergy inducing source. Martin discovers the source is a corsage worn by Mrs. Bentley. Martin manages to get rid of the corsage, and Tim, with Martin's help, proceeds with his painting demonstration to great fanfare. Mr. Bentley deems Tim a major art talent. However Martin announces that Tim has given up on emulating the masters, and will strike out as an artist on his own merit and own style. As such, Tim is a failure. Tim's art career is over, much to his relief.

Martin's present to Tim: a memory machine.

Martin can't decide whether or not to return to Mars.

To prove that childhood is unnecessary, Martin adopts an orphan girl.

On Martian Mother's Day, Martin spots his mother's lookalike.

A Martian drug turns Mrs. Brown into a piano virtuoso.

Mrs. Brown is deluged with suitors after dousing herself with Martian "irresistible spray."

Tim's I.Q. soars when he downs Martin's brain-power pills.

Trouble begins when Tim contracts a Martian virus.

Renowned scientist Professor Newton Jennings posits that life no more advanced than amoebas or jellyfish can exist on Mars. Martin helps Angela write a report refuting Jennings claims, which quickly gets her a failing grade. When Martin's attempts to reason with Angela's teacher fails, Martin figures the only way to regain the upper hand—and Angela's trust—is to expose Jennings as a fraud.

When the junk men come by, they mistakenly empty Martin and Tim's garage instead of Mrs. Brown's, and in doing so take Martin's space ship. Mrs. Brown has no idea the name of the junk yard, but there was a witness to the incident: Booboo, a neighborhood dog. Booboo, with the help of his dog friends and acquaintances, helps Martin track down the junk yard. When Martin and Tim get to the junk yard, they find out that the ship has already been sold to a Mr. Carter, who is using it as a "rocket" carousel at a children's amusement park. Mr. Carter refuses to sell it back to Martin. So Martin decides to disappear and fly the spaceship away, although he does slip Carter the money for the ship anonymously. Martin has one other debt to pay: a steak dinner for Booboo and all his friends for all their help.

Martin can make it back to Mars since Mars has deviated from its regular orbit temporarily and is thus closer to Earth than usual. Martin has a 10 hour window of opportunity. Just as he is about ready to leave, he slips down the stairs and sprains his ankle, which also sprains his disappearing antenna. Mrs. Brown immediately calls an ambulance to the scene. When the ambulance physician takes Martin's vital signs, they rush him to the hospital since his vital signs aren't "human". The intern at the hospital has the same reaction. Martin knows that to get them to discharge him from the hospital, he needs to appear humanly normal and thus does everything he can to have normal human vital signs. He passes that test, but when the doctor requires a fluoroscope, Martin is worried since the gamma rays from which will make him explode. Tim manages to take the fluoroscope for Martin, but the doctors keep Martin in the hospital to figure out why the fluoroscope shows that he has the body of a 20-year old. With one hour to spare, Martin regains the use of his disappearing antenna and manages to escape from the hospital. Just as he is ready to leave Earth for the second time, Martin slips down the stairs once again and sprains his other ankle. Nothing can help him this time and he misses his opportunity to get home to Mars. But Martin surmises that home is where you hang your hat, and that just happens to be Earth for the time being.

Mrs. Brown's niece, Paula Clayfield, comes for visit. A former child prodigy, Paula has always relied on her brains to mask insecurities in her personal appearance. Despite her Plain Jane looks, Paula does have a boyfriend, Dr. Edgar Edgarton (her intellectual equal), with whom she has an "understanding" - they have a commitment to each other shy of a formal engagement. Paula notices Martin's sketches for a space ship, and insists on helping him to refine his design. Later, she also notices in Martin's possession a piece of a Martian alloy (something not available on Earth) to which she states she cannot identify its contents. These probings of course hinder Martin's progress in fixing his space ship as well as his hiding his Martian identity, so Martin asks a reluctant Tim to ask her out to keep her otherwise occupied. After Paula and Tim's first "date", Paula confides to Martin that Tim seems disinterested, which is indeed the case. So to get Tim to ask Paula out again, Martin transforms her into a ravishing beauty without her knowledge. This transformation does the trick on Tim, who continues to take Paula out and eventually asks her to marry him, which convinces her that she can be and is beautiful. Edgar comes for a visit, and after some time he notices the transformation in her appearance, which solidifies their commitment to each other. In the meantime, Paula has accidentally taken Martin's alloy, which she and Edgar are going to get tested. Martin's Martian identity would then be exposed, that is unless Martin and Tim can get the alloy back beforehand.

Martin's duplicating machine creates another Mrs. Brown.

A young boy hijacks Uncle Martin's spaceship.