The Children's Planet is the 33rd episode of The New Adventures of He-Man.
At the Oasis, Caz and Adam dueling each other with wooden sticks, while Mara looks on. They are interrupted when the Scientists arrive and tell Adam that they need to see Master Sebrian immediately. The Scientists barge in and tell Master Sebrian that they've detected Black Omega, a deadly gas that has the power to destroy Primus' shield. Master Sebrian is surprised at this information, because he thought that all of the Black Omega had been destroyed centuries ago. Meldoc reveals that the gas is located on a frozen planet on the edge of the Tri-Solar System, which the Scientists, strongly advocate destroying the entire planet to keep themselves safe. Master Sebrian reluctantly agrees to destroying the planet, but they need the help of He-Man to do so. Caz overhears the conversation and decides to stow away on the Starship Eternia, before it leaves Primus. He-Man, Spinwit and Tuskador, set their course for Omega 4.
Meanwhile on Omega 4, two mutants drive a Snow Tank through the cold weather. It is revealed that the Mutants are Maxus and his two-headed assistant, Zark, who had been exiled by Skeletor to the planet. They are planning to harvest the Black Omega and then use the gas to bargain with Skeletor for control of the Tri-Solar Galaxy. As the Starship Eternia enters proximity of the planet and He-Man regrets that he's going along with blowing up an entire planet, that could possibly have lifeforms upon it. They soon discover that Caz has stowed away on the Starship.
Back on Omega 4, one of Maxus' slaves speak out against his rule. Maxus removes his goggles and uses his Gorgon Vision to freeze the slave, showing the outcome of disobedience. Elsewhere on Omega 4, four children are traveling through the blinding snow, when they are ambushed by a beast named Cuja. The four duck into a cave, where they slide through a tunnel. When they get to the bottom of the tunnel, it is revealed that the four are the children of Maxus' Slaves. Two of them are brother and sister, Krochi and Litha, who are the children of the disobedient man, who Maxus froze.
Back at the Oasis, Master Sebrian has a vision that reveals that there are living beings on Omega 4. Sebrian contacts Spinwit and tells him to not launch the missiles, because there are in fact living things upon the planet. He-Man tells them to land on the planet to investigate. As the Starship Eternia lands, Zark tells Maxus that there are intruders that have landed on the planet. Upon a Priman Snow Tank, the heroes are attacked by a giant robot, controlled by Maxus. Soon Maxus and Zark reveal themselves causing the heroes to defend themselves. In the outcome of the battle, Maxus uses his Gorgon Vision to freeze Spinwit and Tuskador, while causing the ice to break beneath He-Man's feet, making him fight to stay above the freezing water below, while they escape with their prisoners.
When He-Man overcomes his obstacle, he finds Caz being cornered by Cuja. As He-Man attempts to free Caz, the two accidentally fall through the ice tunnel nearby. At the bottom, He-Man and Caz find the titular children. Back at the Gas Mines, Spinwit and Tuskador are forced to become Maxus' slaves. The two make friends with the mystery guy from earlier, that holds the same amulet that two of the children have. Meanwhile the Scientists, not content with allowing Starship Eternia to destroy a planet, have launched a seeking missile as well, that would supposedly change the molecular structure of the Black Omega. Master Sebrian is angered by this news of the Scientists making this decision without his consent.
While the missile travels to Omega 4, Litha explains to He-Man, that they are from the planet of Spira. Maxus destroyed their planet and the survivors were brought to Omega 4, to work as his slaves in the Gas Mines. She also tells him that the four had escaped from Maxus' Prison. When they arrive at the secret tunnels that lead to Maxus' camp, Maxus' attacks and uses his visor to create an two Ice Monsters. Krochi and Caz begin throwing snowballs at Maxus, who accidentally destroys his own Ice Monsters. With that, Maxus uses his Gorgon Vision to freeze He-Man, capturing him.
While Maxus and Zark prepare to leave the planet with the Black Omega, He-Man uses the Power Of Grayskull, to free himself from his icy prison. He-Man challenges Maxus while he is taking off. Maxus uses his Gorgon Vision, but He-Man reflects the beam, stopping Maxus from leaving the planet. Just as Maxus' spacecraft crashes, the missile arrives and hits it, turning the Black Omega gas into laughing gas. Maxus is exiled yet again and the children are reunited with their father. They refuse the chance to come to Primus, because they decide to build a new colony on Omega 4.