Summaries

Synopsis

NASA sends robotic probes to Mars and find evidence of fossilized organic compounds in their rocks. NASA concludes that there was life on Mars in the past. Unknown to anyone, Mars has a thriving civilization underground. Martian babies are born in the ground and are looked after by Nanny bots.The Martians, led by their villainous supervisor (Mindy Sterling) and her junior Ki have been observing Earth mothers, passing up those who are too indulgent or unable to control their children.

Milo (Seth Green) is a nine-year-old boy who constantly rebels against his homemaking mother (Joan Cusack) and workaholic father (Tom Everett Scott), who, himself, is leaving for a business trip. Summer is just beginning, and while Milo wants his summer to be fun, his mother assigns him chores. When Milo's mother catches him breaking her "no broccoli, no TV" rule (Milo had fed the broccoli to his cat Cujo, who vomited the broccoli, as vegetables are poisonous to cats), she grounds him and sends him to bed early.

After a heated disagreement with her, Milo wishes that he never had a mother, which leaves his mother heartbroken. Later that night, Milo feels bad about talking to his mother that way and goes to her room to apologize to her. Milo sees his mom being kidnapped by Martians who plan to steal her "Momness" to rear their own young.The Martians had selected Milo's mother, based on her ability to command Milo to take out the trash.Milo follows the Martians, who had taken his mother to a large spaceship. Milo gets tangled in the landing gear of the spacecraft and is lifted into the spaceship when the landing gear retracts after the ship lifts off.

To rescue his mom, Milo stows away on the spaceship in which his mom is being taken to Mars by the Martians. The spaceship opens a portal to reach Mars within seconds. Upon arrival on Mars, Milo is discovered by the supervisor & her team. The spacecraft lands on the surface but is soon taken underground by a vertically moving platform.Milo is locked up in a jail cell but manages to escape down a garbage chute where he meets a tech-savvy subterranean-dwelling Earthling named Gribble (Dan Fogler). Due to the lower gravity on Mars, Milo discovers that he can jump a lot farther and higher as compared to Earth. Gribble has been hiding on Mars by living in the garbage section of the colony, just below the ceiling of the garbage storage and incineration area. Gribble attaches extra weights to Milo to help him adjust to the lower gravity.

Gribble's home is made from parts that he has salvaged from garbage. He also gives Milo a Martian translator. Gribble has a robotic helper named Two-Cat (Dee Bradley Baker). Wingnut (Kevin Cahoon) is a male Martian and Gribble's friend.

Gribble has been living on Mars for many years. He was the one who helped Milo escape from prison. Gribble tells Milo that Martians hatch out of the ground every 25 years or do & Mars is short of moms to take care of the kids. Martians are terrible at mothering.Martians are good at building robots or Nanny bots. Each Nanny bot gets one Martian kid to raise, and after that they are recycled. But, to program them, they need the memories of a real mom. So that's why they kidnap tough moms from Earth, extract their memories & use it to program the Nanny bots. Martians only care about order and discipline and that's what they look for in Earth mothers before selecting them.

Gribble tries to convince Milo that by sunrise Martians are going to complete the procedure on his mom & there isn't any time to save her, but Milo is insistent. Milo has only 7 hours to rescue his mom, before sunrise. They would have to fight against the Supervisor's Secret Security team known as the SISS.Gribble helps him devise a plan to get Milo attacked by the Martians, when Milo reaches the surface. Gribble does this to get Milo to drop his plan to rescue his mother and to stay with Gribble at his hideout. At a Martian checkpoint, Milo is exposed and the troops raid Gribble's hideout (by tracing the source of the communications to Milo's headset). Milo was being chased by the SISS troops and was relying on Gribble's instructions to run, but somehow Milo manages to escape.

While hiding from the guards, Milo meets an optimistic Martian named Ki (Elisabeth Harnois) who is fascinated with Earth because of all its colors as opposed to the more stern and sleeker Mars. Ki is a rebel against the supervisor as she secretly keeps putting vibrant colors up for public display, much to the irritation of the supervisor. Milo makes it back to Gribble's hideout (where he finds one of Gribble's old t-shirts in his destroyed hideout, which had a photo of his mother. Milo realizes that Gribble would have arrived on Mars as a stowaway just like him) and discovers Gribble has been kidnapped by the Supervisor and the Martians.

After rescuing him with the help of Ki, they take refuge under the tribes formed by Martians who are friendlier and free-spirited. The SISS troops attack the garbage dump (where the tribes were located) and Milo and Gribble escape with the help of Wingnut, by falling down the sewer lines.Now Gribble is afraid to help Milo as he nearly lost his life. Gribble wants to create a new hideout in the sewer section, which is even below the garbage section. But Milo calls him by his real name George Ribble. Milo found a T shirt in Gribble trash that had a picture of him & his mom when he was young & his real name.Gribble confesses to Milo how he wound up on Mars: twenty-five years ago, the Martians selected Gribble's mother as a fine example to program their Nanny bots. Gribble says that he was a good kid, which is why his mother was chosen.Like Milo, Gribble stowed away, but failed to rescue his mother in time and was stranded on Mars. During the escape, Milo and Gribble are separated from Ki. Gribble saw his mother in a spherical container, being hooked to a machine, that was powered by the sun. The Machine was on the surface of the planet and was activated at sunrise. Gribble saw his mother vanish from the container, as soon as the sun came up.Recounting the incident, Gribble is now determined not to let sane thing happen to Milo.

After Ki manages to locate Milo and Gribble in an untouched part of the Martian underground world, they come across an ancient cave painting that showed Martian families were like Earth families in the past. If Martians had parents, they would not have to be raised by machines, and hence they would not need Earth mothers to program them.Ki takes Gribble and Milo to the control center, where they see boy and girl Martian babies being sorted. The girls are assigned Nanny bots and the boys are sent to the garbage section to be raised by the Tribes.After evading the guards and capturing a spaceship, Milo manages to wake up his mother, and save her before the download destroys her. They try to escape, but Supervisor halts them, and is about to kill Milo and his mother. Fortunately, Gribble saves them both and then gets into a fight with Supervisor, who fires a shot that causes Milo to trip and break his space helmet.

As Milo begins to choke in the light Martian atmosphere (not suitable for human breathing), Milo's mother gives him her space helmet. Although Milo's life is saved, the life of his mother has now been put at stake. Before the eyes of the Martians, Gribble (not wanting to see another Earth boy lose his mother) manages to find the space helmet he'd attempted to save his mom with and gives it to Milo's mother, showing the Martians the one thing they had overlooked about Earth moms: love for their children.

Milo soon realizes that his behavior had been very wrong, so he apologizes to his mother, thus showing his new respect and greater love. The Supervisor attacks the Earthlings again and is about to recapture them, but Ki reveals the photo of the ancient cave painting and the Supervisor's deception to the soldiers, causing them to turn against the evil mistress.

With the Supervisor in prison, Ki and Gribble return Milo and his mother to Earth, just before Milo's dad returns home. Having nowhere else to go and having exposed his feelings for Ki, Gribble decides to stay on Mars with her and returns there. Milo then takes out the trash before his mother asks him to, but secretly disintegrates it with a Martian weapon, similar to a human pistol in size and shape. Under the new leadership of Gribble and Ki, the male and female Martians work together in raising their young, while the Supervisor is stuck with Nanny duty. Gribble manages to contact Milo and let him know how he is by using the Spirit rover as a communication station.