"I've been dying to give the Thundertank a real workout, and there's just never going to be a better reason for a trial run!"
With the help of the Berbils, the Thundercats have completed Cats Lair — their home and base of operations — far more quickly than they expected. Unfortunately, they are not the only ones who have been busy. The Mutants have also finished building their own headquarters, Castle Plun-darr. They did not use the help of friends, but instead used slaves, a race of docile, simple, easily-controlled creatures known as Brutemen. The Thundercats are determined not to let them get away with it.
This episode provides examples of:
- Chase Scene: The Thunderkittens lead Monkian on a pretty cool one through treetops.Monkian: You couldn't outrace me in the trees anyway. Thanks for saving me the trouble of chasing you.
- Deadly Dodging: How Cheetara takes out Jackalman.
- Early-Installment Weirdness: Wilykit and Wilykat get themselves out of trouble, gain valuable intel spying on the Mutants that they bring back to the adults, and stay behind when they are ordered to. It is too bad that their characterization couldn't remain this way throughout the series...
- Famed In-Story: Slythe's reaction to meeting Panthro is, "So I face the great Panthro!"Slythe: I am not impressed, panther.
Panthro: You're no work-of-art yourself, you scaly reptile. - Fantastic Drug: Warp Gas. Purpose: reverse the subject's nature.
- Furry Reminder: The Thunderkittens climb and leap between trees like, well, cats.
- Hoist by His Own Petard: The Mutants are defeated by their own warp gas.
- Home Field Advantage: As Monkian tells the Thunderkittens, they have no chance of outrunning him in the trees.Monkian: If you think you'll escape through the trees, you've chosen the wrong route!
- Oh, No... Not Again!: Lion-O says this verbatim after Slythe gives the Brutemen a second dose of warp gas and come after him a second time.
- Poor Communication Kills: The Thundercats have been trying to get the liberated Brutemen to escape from Castle Plun-Darr. But the Brutemen are confused about what they're saying, until...Lion-O: Don't you understand? You're not slaves anymore, you're free!
Brutemen: (rejoicing) Free! Free! (they march back to their homes) - Sheathe Your Sword: Lion-O refuses to fight the drugged Brutemen, but he also refuses to run from them.
- Slavery Is a Special Kind of Evil: The Thundercats are disgusted when they hear how the Mutants have enslaved an entire race. This is clearly crossing a line for them.
- Slippery Skid: This is how the Thunderkittens escape Monkian in the trees.
- Supervillain Lair: The Mutants now have castle Plun-darr to serve as this, thanks to slave labor.
- Technology Porn: One scene is dedicated to showing how nothing the Mutants build can stand up to the Thundertank.
- Too Dumb to Live: The Brutemen, since they have "not much upstairs".
- Ungrateful Bastard: Subverted with the Brutemen, as Lion-O only pointed out how they didn't even say thanks for freeing them. The other Thundercats call him out for expecting something in return. Lion-O denies this, saying that he saved them because "it was the right thing to do".Snarf: Nobody bothers to mention he was just following ol' Snarf's example. Oh no!
- You Meddling Kids: "So, Thunderkittens... the pesky ones."
