The inhabitants of the planet Thundera evacuate just before it is destroyed. They were pursued by a band of mutants. All but one of their escape ships was destroyed. Only a small group of Thunderians (Thundercats) remained. With only half engine power, the group, which was led by Jaga, had to set a course for the nearest planet. Jaga commanded their ship while the other seven were in their stasis tubes. Jaga died on their journey to Third Earth and their ship crashed there. Soon they made friends with various groups in the area and they designed a fortress. Mumm-Ra the centuries-old embodiment of evil, along with the mutants that destroyed the rest of the Thunderians are a constant threat. But Lion-O, the new leader of the Thundercats, with his weapon the "Sword of Omens" will help the Thundercats to have a standing chance.
With their home planet, Thundera, about to explode, the Thunderians flee to a distant galaxy. Before they can make the long journey the Mutants sweep in and destroy most of the fl…
The Mutants, who have also reached Third Earth, encounter an old pyramid. It turns out to be the home of Mumm-Ra the Ever-Living, and they join forces to capture the Sword of Omen…
The Ro-Bear Berbils are a friendly group of robot bears that live on Third Earth. Lion-O and Snarf don't know this, and end up getting caught in a Ro-Bear trap. The Berbils free t…
The homeless Mutants also make plans to build their home. They enslave a primitive race of beings called Brute-Men to do their work for them. The Thundercats go to Castle Plunn-Da…
Mumm-Ra uses his shapeshifting abilities to pass himself off as a Thunderian so he can stage the "rescue" of Cheetara and infiltrate Cats' Lair.
When Snarf and a young unicorn are captured by the pirate Hammerhand and his crew of Berserkers, Lion-O goes to rescue them.
With their supply of Thundrillium running low, the Thundercats set off in search of a fresh supply. Tygra detects a large deposit in a cave and goes to investigate - unfortunately…
Wilykit and Wilykat try to stop a band of living gargoyles from robbing a Wollo but fail to do so and trail the gargoyles to a nearby Tower. Wilykat is trying force the door open …
While investigating an earthquake, Tygra stumbles across the Garden of Delights and meets a talking plant named Silky, who offers him her fruit. But it turns out that "Silky" is a…
Lion-O and Snarf stumble upon a portable jail cell, and mistakenly open it up. Three of the galaxy's worst villains escape. One of them, a slick thief, manages to steal Lion-O's s…
Two Bolkins (sheep-like beings from Third Earth) unleash the ghost of Grune the Destroyer, a renegade Thundercat who once terrorised Third Earth and now turns his attention to the…
Mumm-Ra and the Mutants plot to open the Time Warp Prison and release the evil Princess Ta-She in order to use her deadly Doomgaze against the Thundercats.
When a meteorite made of pure Thundrillium crashes on Hook Mountain, the Thundercats decide to use it to replenish their depleted energy supply. But Lion-O must first gain the tru…
Tired of constantly being bested by the Thundercats, the Mutants have Mumm-Ra raise their spaceship and salvage their vehicles.
Lion-O becomes homesick, and his memories of Thundera are almost nonexistent. Jaga appears to Lion-O and tells him that on their spaceship, they brought with them a time capsule w…
The Mutants, once again searching for a way to destroy the Thundercats, recover some more items from their spaceship. They take their ship's engine and convert it into a giant fir…
Mumm-Ra tricks Lion-O into using the Sword of Omens against Tygra, causing the blade to break in half and lose its powers. The only way Lion-O can restore the Sword is to venture …
Mumm-Ra creates device that can make Panthro clones. He embeds the spirit of Hammerhand into his clone and sets it free to destroy Third Earth. The Third Earth inhabitants blame t…
Wilykit and Kat accidentally free an ancient monster that was banished to an old shrine centuries ago. The evil monster, Mongor, begins to destroy the planet, and is much stronger…
The Thundercats briefly show Lion-O how the time capsule they recovered from the caveman works. Curious to see more, Lion-O activates it during his night-time watch, and gets caug…
An old scientist seeks the Thundercats to help him save the oceans of Third Earth. Long ago, a crack was made in the bottom of the ocean which caused the water to drain into the e…
Jaga is captured by Nemex, an evil being in the Astral World, and Lion-O tries to find a way to rescue him. Third Earth legend says that the only person who can transport anyone t…
The Thundercats think that Snarf is getting too old, and that he is not up to doing as much as he does. To prove them wrong, Snarf saves the Thundercats from another mess. The evi…
An evil hunter lands on third earth in search of prey to hunt. His holographic machine can tell him about all of the Thundercats, including their strengths and weaknesses, and he …
Nearly all the Thundercats have been captured by the Mutants and imprisoned in Mumm-Ra's Pyramid, forcing Snarf to use his own talents to free them.
An alien spaceship crash lands on third earth, and it can somehow communicate with Cheetara through her sixth sense. She becomes a part of the spacecraft, and begins to feel what …
Mumm-Ra summons the great samurai Hachiman to seek and destroy Lion-O. He tells Hachiman that Lion-O and the Thundercats are destroying his planet. Hachiman and Lion-O confront e…
Mumm-Ra has a phial of miniaturization gas. Vultureman builds a mechanical Wolfrat to infiltrate the gas into the Cats' Lair. The ThunderCats are immediately reduced to nine inche…
Vultureman summons Ratar-O to take him to the planet of the Snarfs to capture one of them and use it as ransom with the Thundercats. Snarf, thinking his entire race was wiped out…
The ThunderCats race to try to salvage the part they need for the Feliner from the wreck of the Rat Star before the Mutants can complete repairs. Snarf contemplates leaving the Th…
Mandora, on space-patrol, encounters an old pirate ship which doesn't meet inter-galactic standards. She boards the ship, arrests the pirate, and sends the ship to a space prison…
The Driller, Mumm-Ra's servant who captured Panthro for him in Spitting Image, returns to aid Mumm-Ra once again. His job this time is to drill a hole from the Cats' Lair to the A…
Wiz-Ra, Mumm-Ra's enemy from long ago, comes back every 7000 years through a portal that just happens to be in Cheetara's bedroom. Wiz-Ra wears a magical helmet that lets him con…
Mumm-Ra finds out that the Kingdom of Webs has a new Queen, Spidera. Mumm-Ra thinks he can lure Lion-O into her lair. He transforms into a diamond fairy and casts a spell on Lio…
Mumm-Ra hires Captain Shiner to send a fake distress signal to the ThunderCats. With their new vehicle, the Feliner, the ThunderCats set out into deep space to help the "ship in …
Wilykit and Kat find an ancient harp that has a genie in it. His name is Charr-Nin. Mumm-Ra appears to the genie and tells him that if he destroys the Thundercats, he will be fre…
On Lion-O's 20th birthday, he must pass a set of trials to become the true Lord of the ThunderCats. Even though he is the hereditary Lord of the ThunderCats, he must prove himself…
A vagabond space traveler lands on Third Earth to challenge Mumm-Ra to a fight. The Demolisher is victorious against Mumm-Ra and sends him running back to his tomb. Mumm-Ra ackn…
Monkian goes to Mumm-Ra and agrees to give him anything if Mumm-Ra will make him powerful enough to rule Third Earth. Mumm-Ra agrees, and gives him Power Spheres which make him s…
After the Mutants fail to ambush and defeat the Thundercats with Vultureman's new Thundrainium cannon, Vultureman, furious about the failed attempt and the loss of his weapon, act…
Micrits, a tiny race of human-like figures, happen to live right outside Cats' Lair. Unaware of their existence, Lion-O manages to continuously step on their village and destroy …
On the second day of his trials, Lion-O must race Cheetara through the dangerous lands of Third Earth. Although Cheetara is by far the fastest among the Thundercats, her speed can…
Mumm-Ra awakens the Rock Giant, an ancient monster made of stone which looked like a mountain to the TCats. When it wakes up, Mumm-Ra sends it to destroy Cats Lair. The TCats try …
The normally submissive JackalMan decides to start his own army in hopes of conquering Third Earth by himself. He does manage to give the Thundercats trouble, but soon he is defea…
An evil robot monster is attacking the Tuska Village, in an area unexplored by the Thundercats. Turmagar, the leader of the Tuskas, travels to the Cat's Lair to ask for aid in def…
Wily Kit and Kat stand in Lion-O's way on the third day of his trials. Lion-O must beat them through the maze of infinity. Attempting to stop Lion-O and slow him down, the kids se…
Mumm-ra transforms himself into a ro-bear berbil (a Thundercat ally). He acts hurt and the Thundercats let him stay at Cats Lair. One night, Mumm-ra(the berbil) puts all the Thund…
Panthro invents flying video cameras which are suppose to record the events that take place on third-earth so they could create their own holographic time capsule. Mumm-Ra, in hop…
When a big storm hits Third Earth, the Thunderkittens are trapped in an old space capsule. Meanwhile, Tygra and Cheetra almost crash the Feliner, but Lion-O guides them in for a s…
Lion-O undergoes the fourth task in his Anointment Trial.
The story of Excalibur, the greatest sword in history, is revealed to Mumm-Ra, who is then determined to find the Excalibur and defeat Lion-O and the Sword of Omens.
A giant Ice King is accidentally released from his glacial prison and attacks the Castle of the Snowmen.
A Terator Starship, an extremely ugly spaceship, is pursued by a Kymera Craft, a visually appealing spaceship. The Terator Spaceship escapes and lands at the Cats' Lair
A spaceship freighted with a lethal radioactive sphere is on a collision course for Third Earth.
Vultureman invents a voice imitator that imitates the ThunderCats' voices. He uses it to lure the ThunderCats into perilous situations.
Mumm-Ra transforms into Mumm-Ra the Dream Master and summons spectral Dream Selves from the sleeping Panthro, Cheetara, Tygra, Wilykat, and Wilykit.
Willa is practicing her long-bow skills when a warning device alerts her to a Mutant attack. Willa is captured and the ThunderCats rush to rescue her.
Mumm-Ra summons the Mutants and threatens to banish them from Third Earth unless they bring him the Sword of Omens.
Vultureman invents a Super Power Potion which give him magical powers, enabling him to mesmerize and defeat Tygra.
Jackalman ambushes Snarf and attempts to steal the Sword of Omens. This gives Panthro the idea to make a duplicate sword as bait for the Mutants.
The concluding trial in Lion-O's Anointment Trials pits him alone and weaponless against the evil Mumm-Ra.
To prove themselves worthy of being ThunderCats, the ThunderKittens borrow the other ThunderCats' weapons and practice with them. They are ambushed by Mutants, who take their weap…
The Feliner is attacked by the RatStar, manned by the Mutants. Jackalman, Monikan, and S-S-Slithe are ejected and saved by Mumm-Rana, a female mirror image of Mumm-Ra, who is a fo…
Vultureman invents the Shifter, a device that can switch personalities, and uses it on Panthro's personality and Snarf's body.
Mumm-Ra creates a museum where painting and statues come alive to oppose the ThunderCats.