Bengali is one of the three Thunderians found living on Third Earth. Bengali is a Blacksmith by trade, a craft taught to him by his father. He later uses this skill to reforge the broken Sword of Omens. Bengali is quick and agile like Tygra and wields the Hammer of Thundera. The Hammer of Thundera can shoot blasts of energy and also carries smoke pellets in the handle, which Bengali uses to cause confusion and provide cover.

Pumyra, another of the new Thundercats, is a healer and medic who chooses to solve conflicts without fighting. Pumyra has an incredible leaping ability and agility and uses a "cat tail" whip-cord to launch pellets like a sling. Pumyra is one of only three females within the Thundercats.

Lynxo is the third and oldest of the new Thundercats. Lynxo was blinded during the escape from Thundera and relies on his other senses to get by. His hightened senses allow him to find pressure points which he uses to disable his enemies and also to feel vibrations which allow him to avoid attacks. Lynxo's weapon is the Sonic Reflector.

Jagana is an ancient and immortal Thundercat who lives in the core of New Thundera. Jagana guards the gyroscope to keep New Thundera intact and uses the power of levitation, teleportation and psychokinesis to ward of enemies.

Other Good Guys

• Snarf — An elder snarf, properly known by his name Osbert (which he hates), Snarf served as a nursemaid and protector for Lion-O when he was a boy. After Lion-O grew up, Snarf found that often Lion-O didn’t want to have him ‘mothering’ or protecting him. Still, Snarf has remained loyal to Lion-O and the other ThunderCats. At times, he does come through in the crunch with an idea or taking action when it is needed, and despite his age he does keep up with the others.

Even though not a fighter by skill or nature, Snarf is very agile (he boasts he can outplay anyone at tailbail or kick-the-bucket). He also can communicate with other animals on Third Earth to enlist their help in his tasks and adventures.

• Snarfer — Young and excitable, Snarfer is Snarf’s young nephew. He was thought lost when Thundera exploded, but was one of the surviving Snarfs that made it to the Planet of Snarfs. Slightly more aggressive than his uncle, Snarfer is a keen mechanic and pilot in his own right (Snarf once said he was a ‘college boy’). He does tend to babble when over-excited, but at times he can be just as level-headed as Tygra. Though smaller than Snarf, he doesn’t let that get in his way when he wants to help friends. It was through him that the ThunderCats learned that Snarf's real name was Osbert.

• Snarf Oswald — Mentioned by name and later appearing in the episode "ThunderCubs Part 3", Snarf tells the others that this particular fellow ‘owes him fifty Thunder-Dollars from their last tailball game’.

Many other unnamed Snarfs were also featured in the 5-episode "ThunderCubs" story, where they were enslaved by Mumm-Ra on New Thundera. Two of these were relatives of Snarf Osbert and Snarfer, and were later rescued by the ThunderCats.

• Ro-Ber-Bill and Ro-Ber-Belle — Leaders of the nearby Ro-Bear Berbil village, these robot-bears are the first to befriend the ThunderCats and often supply information about local places, people and phenomena on Third Earth. Through their fields and forests of Fruit Trees, they are also able to provide the Thunderians with new foodstuffs.

• The Ro-Bear Berbils — Partly-furred mechanical bears from the planet Ro-Bear. Because their homeworld is so tiny, they must form other colonies on distant worlds to survive. Small and harmless looking, the Berbills are steadfast, hardy workers and skilled farmers, cooks and craftsmen. It was thanks to them that Tygra was able to build Cat’s Lair — and later the Tower Of Omens — so quickly.

• Willa and Nayda — Sisters, both members of the Warrior Maidens, who live in the Tree-Top Kingdom. Willa is their leader, while Nayda is a scout and second-in-command. Both are expert markswomen with bows and arrows, and are very agile and fleet among the branches of their forest home. Often distrustful of outsiders, both become friends of the ThunderCats and by their example, the rest of their people treat them as allies. They often help the Thunderians by showing them paths around Third Earth and using special tricks (like Bushy, a giant tree-top spider) to aid them on their quests and missions.

• The Warrior Maidens — A race of Amazon women who live in the forests of what is called the Tree-Top Kingdom. They are fierce fighters and very territorial. At first distrustful of the ThunderCats — whom they view as aliens — the Warrior Maidens soon treat them as friends. Often, Nayda and Willa are the two that have the most contact with the ThunderCats.

• Wollows — Small, furry people who have small villages all around the habitable places of Third Earth. Farmers, carpenters and fishermen, they are gentle folk who often turn to the ThunderCats for protection.

• Bolkens — Sheep-like people, similar to the Wollows. They are herdspeople and farmers, who are just as likely to call for help from the ThunderCats.

• Mandora the Evil-Chaser — An intergalactic police officer, who works in conjunction with a series of law enforcers to protect the peaceful people of the galaxy. She works in part to run the Great Penal Planet — which houses some of the galaxy’s nastiest criminals — and routinely comes to Third Earth as part of her patrols. When one of these criminals, a robotic pickpocket named Quik-Pik, helps her and Lion-O against Captain Cracker, she makes him an Evil Chaser assistant. She travels on a specially-equipped hoverbike — called the Electro-Charger — and uses a weapon called the “enzyme catalyzer” (a spray gun that uses a chemical — "a closely guarded secret, once called soap").

• Hachiman — A samurai warrior and master swordsman from Ancient Japan. Summoned to Third Earth by Mumm-Ra, he was tricked into fighting Lion-O, but thanks to his code of Bushido, he became an ally to the ThunderCats and the Warrior Maidens of the Tree-Top Kingdom. He wields a sword known as “The Thunder-Cutter”, a katana-blade that, with his skill, can cut through solid stone.

• Snowman of Hook Mountain — A yeti-like chivalrous knight , who rules over the Kingdom of the Snowmen on the frigid heights of Hook Mountain. He once tried to fight Lion-O for possession of a meteor that fell onto the slopes of his mountain kingdom, but they became friends after Lion-O rescued him from a Mutant attack. He can craft weapons out of ice, seemingly at will, and fights mounted on a great snow cat, Snowmeow.

• Turmagar — Leader of the walrus-like Tusken Warriors who live near the source of the river that serves as Third Earth’s natural water supply. Very skilled as a warrior and leader, Turmagar is also a crafty pilot who flies the Gomplin —- a vehicle/creature hybrid. It is Turmagar who often helps the ThunderCats with air support before they crafted their own air-vehicles. (It is worth noting that the Tusken Warriors are among the few factions in the series to employ firearms, as opposed to melee weapons and/or bows and arrows.)

• Dr. DomeTome — One of Third Earth’s great thinkers, scientists and gentlemen. He is the chief protector of the Great Oceanic Plug, a massive engineering project built to seal a crack in the ocean floor to prevent the planet’s oceans from flooding its core. He is a small man but very chivalrous, and a skilled pilot of Hercules (aka "Herky"), a giant frog-shaped robot used to guard the sea floor.

• Wizz-Ra — A powerful wizard from Ancient Egypt, banished to an alternate dimension after he lost a battle to Mumm-Ra. His helmet has the ability of mind-control and is sought by Mumm-Ra after it’s discovered that the wall of the Seventh Dimension is weak enough (after 7,000 years) for him to appear in Cheetara’s bedchamber. He aids the ThunderCats after they help him to recover his helm, and then is forced to return to his dimension prison, though not before promising Cheetara they would meet again in her dreams.

• Mumm-Rana — An ancient sorceress for good, and counterpart to Mumm-Ra. She lives in the White Pyramid, where her powers keep her from traveling too far. She at one time battled Queen Luna (grandmother to the Lunitac Luna), to stop her rampage across Third Earth. She did so by stripping Queen Luna of her magical belt, which she later lost to Luna (which was destroyed eventually). Much like Mumm-Ra, her powers limit the time she can spend outside of her pyramid home.