* {{Anvilicious}}: Like a lot of [[TheEighties 80s]] cartoon series, a lot of this show's episodes were focused on some specific "moral", and weren't very subtle about it.
** Somewhat justified in that Lion-O needed to be taught these lessons and quickly so he could become an effective leader.
** And sometimes a little [[{{Narm}} Narmy]], like in one episode where Tigra practically [[NoFourthWall looks at the camera]] when stating the how laws that go unobeyed "are just words." You know, [[IdiotBall rather than rescue their leader]] from a mob of BrainwashedAndCrazy natives.
* AssPull: Some characters (including Lion-O) somehow get massive powers on convenient moments, like Cheetara's psychic LimitBreak.
* BizarroEpisode: Most of the William Overgard episodes tend to be this. One episode had Lion-O go to another planet without the Sword of Omens, defeat the Lunatacks with common household products, and then he was able to summon the sword from all across the galaxy to the planet he was on and flew back to Third Earth with it.
* EnsembleDarkhorse: Panthro is regarded by many fans as their favorite.
** Tygra also garnered some decent popularity, especially with girls watching the show. He was the Thundercat besides Lion-O to get a new figure in Bandai's line of classic [=ThunderCats=]. Many of his fans were upset by the changes made to his personality in the 2011 reboot.
** Pumyra was under-utilized because the producers often didn't know just what to do with her, but many fans claim her as their favorite character. The anticipation surrounding her appearance in the 2011 reboot is ''insane.''
** Grune was one of the more popular villains despite a handful of appearances.
** Alluro was pretty well-liked even by fans who hated the season 2 cast additions.
*** Ditto Lynx-O.
* EvilIsSexy: Chilla
** Also, Ta-She. Even Lion-O thinks so.
* HamAndCheese: Mumm-Ra, so very much so.
* HilariousInHindsight: Early in the second season of the [[WesternAnimation/ThunderCats original '80s show]], Lynx-O tells Lion-O that his voice sounds just like his father's. In the [[WesternAnimation/ThunderCats2011 2011 remake]], Larry Kenny, Lion-O's original VA, is the VA for Lion-O's father, Claudus.
* MagnificentBastard: How Mumm-Ra managed to screw Monkian over in the episode "Monkian's Bargain."
-->[[spoiler: '''Mumm-Ra''': "You rule Third Earth. But it is a kingdom you will never see! [[AndIMustScream Because you can never leave my pyramid]]!"]]
* MemeticMutation: Mumm-Ra likes to watch.
* NightmareFuel: Mumm-Ra, period.
** As creepy as Mumm-Ra was, the Living Ooze was definitely the scariest thing on the show.
** A nightmare-tastic episode has Lion-O was trapped in some creepy catacombs with these Morlock-esque creepers with gigantic eyes, speaking about how they had been driven out of the world by people being too terrified of what was written in their books.
** Tygra becoming addicted to the Keystone, becoming both paranoid, insane and losing a lot of weight along the way. For an 80s cartoon to depict not just the mental damage but also the physical damage addiction, any addiction, could do to someone and do it so graphically is as impressive as it is creepy.
*** The wild and crazy dream sequence Tygra had when he got hooked on the Silky Fruit is also pretty damn creepy.
** In addition to all the eerie figures encountered in the cave of the Nether Witch, an infernal hand kept appearing with a dissuading gesture, as if trying to warn Lion-O not to proceed further.
* TheScrappy The entire Snarf race
** Since they're supposed to be "normal" where they come from, AlienScrappy also.
** Special mention should go to Snarfer, who was just downright annoying. Also the three new [=ThunderCats=] from season 2 weren't very well-received.
*** Judging by the new animated trailer, they may be attempting to [[RescuedFromTheScrappyHeap rescue Snarf from the Scrappy heap]]. They were actually able to do this by changing the Snarf race into a species that ''doesn't talk''.
** The character probably most deserving of fans' hatred is Captain Bragg, who made the Mutants and Lunatacs look like a bunch of chumps (well, more so than usual) and [[PutOnABus put them on a train out of the series]]. He gets away with hypnotizing [=WilyKat=] and tricking him into helping him and doesn't get punished for it. Bragg doesn't even have any real coolness to him to make up for it, he's just an old circus ringleader with a talking crow.
** Weirdly enough, Tygra of all characters was apparently this to the original series head writer Peter Lawrence, who considered Tygra "boring" (and because of it Lawrence reportedly shipped Cheetara with Lion-O rather than Tygra). Lawrence didn't think too highly of Pumyra either, which is why they both got PutOnABus (or rather left behind) in the fourth and final season (with Tygra's final appearance forcing him to carry the IdiotBall).
* TheyWastedAPerfectlyGoodPlot: In one episode, Monkian's comrades ask him where he's getting his info on the [=ThunderCats=]. He smugly explains that he's seeing one of the Warrior Maidens, and she's TheMole. [[WhatHappenedToTheMouse This revelation is never brought up again.]]
** Mumm-Ra sets up a plan to lure Lion-O to an area where his most formidable opponents will be waiting for him. Summoning Slythe, Safari Joe, Spidera, and (just to make sure) Ratar-O, it was explicitly stated that Lion-O was to face them [[VillainTeamUp combined]] as each gave him a hard time in the past so there was no way he could conquer them all at once. He only ends up fighting two of them, and separately no less.
** "Telepathy Beam" has Cheetara receiving a startling vision of the Mutants making short work of the Berbil village with more brutality than seen before and [[FromBadToWorse then]] Skytomb itself arrives on the scene. So disturbed is Cheetara witnessing their plight that Lion-O vows to settle things once and for all. The whole thing turned out to be a false alarm which suited the episode's plot, but considering how exciting the scene was and the less than thrilling send-off the villains actually got in a later episode; it's a shame it wasn't real after all.
* UnintentionallySympathetic: The Mutants of Plun-Darr - Slythe, Monkian, Jackalman, Vulture-Man - even though they're evil they're just so BlessedWithSuck that sometimes you just can't help feeling sorry for them. [[spoiler:This is not the case with their 2011 counterparts, however.]]
** Mumm-Ra, himself, in the later seasons. Despite his evil goals, he really works and plans tirelessly to achieve them and please his dire masters, while all the Thundercats seem to do is just keep using The Sword of Omens over and over to inexplicably and conveniently undo all his efforts.
** This was [[UpToEleven taken up to eleven]] in the last episode of the five-parter "Return to Thundera", when finally convinced he had succeeded despite all odds and hero ass-pulls, he was suddenly faced with the Ancient Spirits of Evil's wrath for his failure, and could only say: "I..I don't understand!". At that moment, the show felt less like "good will always triumph over evil" and more like watching the desperate struggles of one being against an elitist group with a handheld plot-device.
----