The Mutants are so far have been shown to be enemies to the ThunderCats and have went out of the're way to seek out and try to destroy them.
The mutants come from the planet Plun-Darr. Using their Mutant Mothership, they chased the ThunderCats to Third Earth, which the cats crashed on. Since then they have been seeking to get the ThunderCats.
The mutants are noted for routine schedules of attacking the ThunderCats Cats Lair every Wednesday and Barbastella's Bat Castle every Friday. In addition to that, Vultureman bullies the Bolkins regularly, too.
Later, the mutants after defeating Ratar-O with the ThunderCats end up allying with Mumm-Ra after he gets the Sword of Plun-Darr. This allinace lasts until the mutants failed to defeat the ThunderCats as they take back over the Cats Lair and turn it into Thunder-King-Battle-Lord mode.
- Slithe - He is the leader of the mutants, ruthless.
- Vultureman - He is the mechanic of the group. He has been shown to be the most competent of the mutants.
- Monkian - He is the muscles of the mutants.
- Jackalman - He is the fighter of the group. He is somewhat dumb as well.
- Ratar-O - He was the leader of the Mutants when they tried to takeover Thundera. He has a huge ego and is obsessed with the Sword of Plun-Darr.
- Rat-Bots - They serve Ratar-O and battle for him.
- Club - Used by Jackalman, more than once.
- Morning Star - Monkian main weapon, used more than once by him.
- Ball and Chain Flail - Used by Monkian once in combat.
- Double Sided Axe - Used by Slithe once in combat.
- Clawed Staff - Used by Vultureman once in combat.
- Sword of Plun-Darr - Used by Ratar-O as his main weapon, it was used against Jaga back on Thundera before it exploded, which was caused by the sword itself. Later, Ratar-O had gotten back the sword and was using it on his visit to Third Earth before Jackalman launched it in its chair off the Ratstar.
- Rat's Eye - Used by Ratar-O, the pair of daggers have some powers as well. Usually used as a warm up or in place of the Sword of Plun-Darr, they are far less powerful.
- Seeds of Plun-Darr - Seeds to unleash a deadly plant that would take over the planet, much like it was suggested it did on the Plun-Darr planet.
- Mutant Mothership - Was shown in use when attacking the ThunderCats when leaving Thundera. When the ThunderCats crash landed on Third Earth, the ship was still used to attack them. The ship was later swatted by Mumm-Ra. The status of the ship since then is unknown.
- Sky Cutter - A flying device with a laser on the front.
- Flying Machine - A red airplane that can transport the four mutants.
- Fistpounder - A vehicle that was designed to smash things.
- Mutant Car - The getaway car of the mutants. It can hold all four, but it appears to have no major battle abilities.
- Mutant Buggy - A terrain type of vehicle, it can hold all four mutants. It doesn't appear to have any battle equipment built in, but it seems to be agile and tough.
- Ratstar - A large vehicle that Ratar-O uses. It can travel in space.
- Castle Plun-Darr - The place that the mutants call home on Third Earth, it is equipped to battle those ThunderCats.
- Plun-Darr - The planet they came from. Not much is known about it.
- Exodus, Part 1
- Driller (briefly)
- Secret of the Unicorn
- Panthro Plagiarized! (only Vultureman)
- Lost Sword
- Working Grrrl (only Monkian)
- Jaga History
- Adopt a Jackal
- Summer Fun Day!
- Safari Joe (briefly and only Vultureman and Monkian)
- Snarf's Day Off (only briefly Monkian)
- Mumm-Ra of Plun-Darr, Part 1
- Mumm-Ra of Plun-Darr, Part 2