A strange new world rises from the old: a world of savagery, super science, and sorcery. But one man bursts his bonds to fight for justice! With his companions Ookla the Mok and Princess Ariel, he pits his strength, his courage, and his fabulous Sunsword against the forces of evil.
As Lethal as It Needs to Be: The Sun Sword could cut through inanimate objects and Mecha-Mooks as if they were tissue paper. But the moment he tried to strike down a living foe, the Sun Sword inexplicably didn't work. (At least the writers lampshaded this by having Thundarr express surprise, dismay or both at this.)
Author Appeal: Kirby's character designs for the leads can be easily found online. One of them is of Ariel naked, for sheerly gratuitous reasons.
Thundarr made sure never to use his Sun Sword on a living creature. He would not start in with the hack-and-slash until after he discovered that his enemies were robots; just to make sure we in the audience understood, he would then bellow, "They are machines!"
Fun with Acronyms: An In Joke. Ookla (the Mok) is named after the University of California, Los Angeles → UCLA → "ookla".
Never Say "Die": "Destroy" was used in reference to humans and other living beings oftentimes when "kill" was clearly meant.
No Indoor Voice: Thundarr speaks in an almost perpetual shout. Ookla's growls aren't exactly quiet either.
Non-Human Sidekick: Subverted quite hard compared to the standards of its contemporaries. He-Man had Orko, the Thundercats had Snarf, and Thundarr had... Ookla, a 9-foot-tall, perpetually enraged sasquatch man whom "cute" and "whimsical" don't quite fit.
This might be debatable, considering how often Ookla filled the "comic relief" role.
Poorly Disguised Pilot: Two, one for a trio of super-powered women and another for a teenage gender-flipped version of Thundarr and Ariel (while poor Ookla is represented by their steed, an annoying mutant vulture-lizard with two tails)
Ragnarok-Proofing: It's very doubtful that the working machinery and the wrecked cars that everybody tosses around like footballs would be anything but dust in the year 3994, unless the world-ending cataclysm had, as one of its side effects, the stoppage of rust formation.
Sci-Fi Writers Have No Sense of Scale: It would probably take millions of years — not the couple of thousand years that it takes in the show — to create a population of different, apocalypse-adapted species.
They are mostly modified by magic. So, A Wizard Did It, literally. Only one (non-robot) monster was explicitly non-magical in origin; a genetically engineered relic from the Science Age.
The "two thousand years" mentioned in the opening — when most of the ruins look like they're less than two hundred years old— probably qualifies for No Sense of Scale too.
The runaway planet that passed between the Earth and the Moon appears to have stripped away much of the Earth's atmosphere. The resulting damage to the environment probably arrested the deterioration the ruins would have experienced so we don't get the full Life After People effect.
Lest we forget, a "runaway planet passed between the Earth and the Moon." The thing that whizzes by is not only going at a ponderous speed for an interstellar body, but also seems to only be about the size of the moon itself. And you thought arguing over Pluto being considered a planet was rough!
However, the moon is over five and a half times as massive as Pluto. Anything moon sized pretty easily qualifies as a planet — in terms of scale, at least.
The "runaway planet" is shown cracking the moon with its passing, and ripping away Earth's atmosphere. "Man's civilization being cast into ruin!" would be the least of the problems for any lifeform still alive after that.
Shadow Discretion Shot: Pretty pointless one, too. We see the woman turn into a werewolf onscreen, then we see her shadow changing before she turns to attack a helpless human.
What Measure Is a Non-Human?: Because most of the enemies are mutants and evil disfigured wizards, our heroes are pretty much free to attack them, although dismemberments and mutilations are usually only reserved for robots.