Jail Bake: How Lion-O and Tygra escape their cell when Locked In The Dungeon, via a key in some soup, placed by a Lizard mook whose life they had saved earlier.
Just a Machine: The Soul Sever considers the little insectoid robot Flicker to be nothing but a bunch of wires and circuits without a soul. Flicker's Heroic Sacrifice at the end makes the Soul Sever wonder whether it's more complicated than that.
King of Beasts: The royal bloodline and chain of succession belong to the Lions, something that Tygra is plainly jealous of, and Grune takes issue with.
Last-Second Word Swap: Done for dramatic effect in Episode 17. In the flashback sequence for Tygra's childhood, Lion-O had yet to be conceived when Tygra was adopted into the Thunderan royal family. As a child, the queen would call Tygra her "handsome, little prince." However, upon telling Tygra of Lion-O's upcoming birth, she uncomfortably swaps out "prince" with "darling" when she's about to address him as such again, realizing that Tygra would no longer be first in line for the throne with Lion-O as their first-born heir.
Law of Inverse Fertility: In "Native Son" a flashback reveals that the king and queen of Thundera tried to have a child for years. It got so bad that the queen worried she might be infertile. Their concerns were put to rest when baby Tygra literally flew into their lives in a balloon. So of course just when the royal couple have gotten comfortable with Tygra inheriting the throne as crown prince, the queen became pregnant. Then she died in childbirth, so little Tygra lost his mother and the throne in one night.
Law of Inverse Recoil: Averted for comedy in "Between Brothers", where Wilykat uses a discarded Lizard BFG on a Humongous Mecha. Three Lizards see him struggling with it and try to sneak up on him, only for the recoil to launch him backwards into them, knocking them out.
Lecture As Exposition: During Lion-O's Rite of Passage, his father bellows a ritualized oral history of Thundera at him while taking swings with the Sword of Omens. Lion-O's stuck with a practice sword.
Leeroy Jenkins: Lion-O starts off following this mentality, but he eventually learns the value of thinking ahead and using stealth.
The "sneak up on the enemy so we can take them by surprise" plan in "Into the Astral Plane" was working perfectly, until Wilykit drew everyone's attention by jumping up and yelling at the bad guys for threatening Ahburn.
Leitmotif: The series has one based on the theme from the original show, along with several for characters like Lion-O, Cheetara, the Thunderkittens, Mumm-Ra and the Thundertank.
Light Is Not Good: From the instant Lion-O leaves the upper-city's bright streets and the camera drops to the slums, the viewer knows something's rotten in Thundera
Like Cannot Cut Like: In "The Duelist and the Drifter" Lion-O fights a duel with an interim sword crafted by the same blacksmith who made his opponent's blade. It breaks, since it took years to make the latter and an afternoon for the former.
Limited Wardrobe: Played With. The cast wear the same outfits on consecutive days, but some get organic changes (Grune has an Evil Costume Switch, Lion-O and Tygra armor up, Wilykat and Kit steal clothes to replace beggars' rags). Walking the Earth and uniforms justify the cast's fixed outfits, but doesn't explain why younger versions wear identical clothes in Flashback.
Loophole Abuse: In Lion-O's trial for his life, he had to face against Spirit!Panthro and get him out of a circle. Near the end of his time, he has a Eureka Moment when he realizes as King and Panthro his General, he can order Panthro out. It works.
Lost Colony: The Precursors to the all the sentient Animals of Third Earth are refugees of a command carrier crash.
Lost Technology: To the point that many Thunderians believe technology to be a fairy tale for cubs. Lion-O believes otherwise... and the Lizards know so, much to the woe of Thundera.
Loyal Phlebotinum: Only Lion-O appears able to utilize the Sword of Omens' "Sight Beyond Sight" Though others may take custody of the blade, it's enchanted against "being touched by the hands of evil," which appears to be a failsafe against Mumm-Ra's using it.
In "Omens Part 2", the unfortunate fate of the Lizard scavengers who were caught by the Cats. Seems to be standard practice in Thundera.
In "Berbils", the Berbils are attacked by slavers, a routine occurance due to their peaceful nature and lack of citywide defenses.
In "The Curse of Ratilla," we find out that this happened to most of the survivors of the siege on Thundera, including Pumyra. The experience initially left her rather...bitter.
Magic Feather: Lion-O's temporary replacement sword, needed to win a duel, is not the perfect talismanic object he first assumes, but simply a vehicle for him to employ newly learned skills, as he's made to realize when the blade breaks in half while he's pressing his advantage.
Magic Knight: With a strong dash of Kung-Fu Wizard to boot. Jaga and his clerics combine combat with sorcery to perform super-feline feats.
The Magic Versus Technology War: So the Cats have a magic sword with a magic stone and some magic clerics, and the Lizards have loads and loads of technological superweapons... andThe DreadedEvil Sorceror who is infamous as a foe of the Cats, and would really like his magic stone back now. These odds are looking really stacked.
Later on, the lines get much less clear, as the Thundercats use more and more technology to supplement their magic, and Mumm-Ra focuses more and more on his magic. For example, Tygra chooses to use a blaster, a whip, and a cloaking device frequently, Panthro has mechanical arms and is extrordinarily proud of the Thundertank, and several of Lion-O's magic devices appear to be more along the lines of Magitek than purely magical.
Malevolent Architecture: "Journey to the Tower of Omens" has a video game-style Temple of Doom that Thundera's Clerics created to guard the Book of Omens so that no one else would access it. (hence the gratuitous sharp objects) Anyone else would have a hard time not getting ground into hamburger.
Mount Plun-Darr is definitely the case. Not only is it covered in a near-permanent thunderstorm, not only is it covered in giant red spikes, not only does it have a colossal skeleton covering a good portion of it, but the entire place is cursed so that any who try to find the treasure inside will die.
During Claudus' Viking Funeral, Wilykit unwittingly provides accompaniment on flute somewhere in Thundera's ruins, while Lion-O carves the royal emblem at the base of his father's destroyed monument and eulogizes him with "Rest now to rise again, father." Tygra adds "May your next life show you peace."
Medieval Stasis: Thundera, which has magical swords and clerics, but really hasn't put much thought into moving beyond your standard ancient siege engines. This comes back to bite them hard during the siege in the opening two-parter.
Merciful Minion: When Locked In The Dungeon, Tygra and Lion-O see that a Lizard they saved from a lynching is serving them soup. Lion-O rants about his betrayal, while the Lizard, head low, mumbles that he's cooked a "special" meal
Mid-Season Twist: Episode 7, "Legacy" is when we learn the history of the ThunderCats, the exact nature of their historical conflict with Mumm-Ra, and the game changes. They don't just need the Sword and Book of Omens, now they need to unite the Animals and find three other mystical stones.
Might Makes Right: What many characters, good and bad, seem to believe, including most of Thundera, save for Lion-O who opposes this ideology. The series tries to deconstruct this by showing how this sort of philosophy ultimately creates long lasting grudges and causes more problems than solves them. Thundera is destroyed primarily because of this, and its up to Lion-O to change things. This is, of course, Mumm-Ra's way of thinking.
Mirror Monster: Lion-O's vision in the Blade Reflection of the Sword of Omens takes this form, as he sees a sudden, frightening image of Mumm-Ra's red eyes and fanged face.
Mirror Scare: Inverted. Silhouettes playing across the reflective surface of a geode are meant to startle the viewer after Snarf finishes pulling faces at himself and wanders off.
Missile Lock On: Lizards place beeping devices on pillars and Claudus' monument. They're remote homing beacons.
The Missing Faction: With Thundera's ruination, the Cats are no longer major political players, with Lion-O's tiny group of ThunderCats more immediately concerned with Mumm-Ra's defeat.
Moment Killer: In "Song of the Petalars" Lion-O and Cheetara sit at a small fire, and she takes his hand to comfort him in his pessimistic depression. Snarf picks that exact moment to fly into Lion-O's lap, who informs him that this had better be very important! Later in the same episode, the ThunderCats freak out the Petalars in the middle of a community Rite of Passage ceremony.
Monumental Damage: The Siege of Thundera leaves Claudus' monument as a pair of feet, and the great Sphinx's head lying smashed by its body.
Mood Whiplash: At the end of "Between Brothers", Panthro loses both his hands for throwing Grune in the collapsing Astral Plane. Then the scene shifts to a party and Panthro yelling at Snarf for being a nursemaid. Would it hurt to be a slight bit serious?
Which causes friction later on. The Lizards are fighting for better living and for revenge against the Cats for years of oppression, but surprising numbers of them simply desert and return home to their families in part because Lion-O's group beats them, but also because Mumm-Ra treats them like mooks. When General Slythe brings this up, Mumm-Ra states flat-out that the lizards are mooks, and that they need stricter control to prevent rebellions.
Motive Rant/Screw You, Elves!: A stockaded Lizard prisoner bristles while giving Lion-O a Freudian Excuse for scavenging the Cats' crops: They have little land and resources of their own, thanks to the Cats' expansionism and strongarming. They scrape by while Thunderians throw lavish feasts.
The ancient history of the ThunderCats as related by King Claudus roughly mirrors the plot of the original series. The Lizard's weaponized giant robots evoke those of the original.
In "Song of the Petalars," a Lizard notes "you can't fight what you can't see," quoting the original's Ninja verbatim.
In "Old Friends", Panthro tells Lion-O, "You're standing on my samoflange." Shortly thereafter, Tygra asks, "What's a samoflange?" referring to the infamousouttakes reel from the original series, which includes a similar (but considerably more profane) exchange.
In "Old Friends," after he proves his mettle, Lion-O asks Panthro if he can drive the Thundertank, only for Panthro to reply with, "Not a chance." Lion-O wasn't allowed to drive it in the original series either.
In "Journey To the Tower of Omens," Tygus' ship is a redesigned Feliner from the original series.
In "Berbils," Conquedor shows off a pale blue sabre-toothed cat from Hook Mountain that he captured for the slave auction. This is Snowmeow, the companion and battle steed of Snowman of Hook Mountain from the original series.
In "Berbils", Lion-O completely messes up trying to say "berbil" the same way he did in the original series.
In "The Trials of Lion-O" near-death Lion-O faces against images of the ThunderCats to prove his worthiness much like he had to in the original series' Anointment Arc.
Mount Plun-Darr is very reminiscent of Castle Plun-Darr from the original series, tall and menacing with a giant winged creature.
In "The Forever Bag", the password to enter the bag is "Rankin-Bass!" Rankin-Bass is the animation studio that distributed the original series from 1985.
In "Recipe for Disaster," Ponzi is a Wolo, one of the friendly races of natives on Third Earth in the original series. Also, Tygra's behavior after drinking the love potion is reminiscent of his 80's counterpart's reputation for falling victim to various mind-altering substances.
The Sword of Omens, as well as the Sword of Plun-Darr.
"The Duelist and the Drifter" has many swordsmen who brag about the names and histories of their swords, the most relevant being the Duelist's current best blade, the Sword of Hattanzo.
Ratar-O wields the Rat Eye Daggers, though they aren't named within the show.
Nameless Narrative: In-story, The Drifter tells Lion-O a tale of the Duelist's best sword, giving the characters in it no names, but only descriptors. "The Duelist and the Drifter" is itself an homage to these types of narratives in the Western genre, with its careful avoidance and obscurance of proper names for people, places and things.
Not Now, Kiddo: Inverted. Rather than dismissing Lion-O, Jaga is attempting to indulge him, allowing Lion-O to get back to a party and cheer himself up. Problem is, unbeknownst to either of them, Lion-O's information is very time-sensitive.
Offscreen Moment of Awesome: "Old Friends" shows Panthro and Grune being chased by a giant monster. Cut to them eating heartily as a giant piece of meat cooks on a spit, and its severed head sits nearby.
It looks like all the high-tech lizard toys came from Mumm-Ra's pyramid, once he was released. Panthro also presumably found the Thundertank in the depths of the pyramid, but where he got his knowledge of engineering and mechanics is anyone's guess.
In "Omens Part 2," there are several consecutive examples. Grune gets one when Claudus reminds him of Jaga's clerics. and again when Claudus goes after him in order to get to his friend Panthro It wasn't worth it.
There's also the Cats' en masseOh Crap when the Lizards launch missiles at Thundera The Cats don't even think these things exist! The real life equivalent would be someone launching a fireball from their hands. which Mumm-Ra promptly does. And speaking of
The moment Jaga sees Mumm-Ra. The Cool Old Guy is visibly trembling and sweating.
Jaga: The day I have always feared has finally arrived.
Lion-O when he sees Pumyra give Mumm-Ra the Tech Stone, then kiss his hand while calling him "master".
In "Omens Part 2" Mumm-Ra pulls off an impressive one with a Kamehame Hadouken, devastating the Clerics.
In "Old Friends" Grune and Panthro fast-track themselves to Captaincy by using a catapult to kill Lizards massing on Claudus.
One-Woman Wail: Marks when Lion-O notices a Petalar dying as they travel through the Briar Woods.
Only the Chosen May Wield: The Eye of Thundera, the stone in the sword judges the worth of the candidate in a Rite of Passage meant to test if a candidate can see visions within it. The Sword of Omens is itself generally enchanted against "being touched by the hands of evil," much to Mumm-Ra's consternation.
The Only Way They Will Learn: The Drifter keeps telling and showing Lion-O what he ought to do about or against the Duelist (as much as an eccentrictrickster is able), but when it doesn't sink in, he relents and helps Lion-O by facilitating a rematch.
Cheetara (and to a lesser degree Tygra) gets one in "Into the Astral Plane". Tygra has some more focus relating to his sibling rivalry in the following episode.
Tygra gets more focus in "Native Son," where we finally learn of his birth clan, and how he came to be adopted by Claudius.
In "Survival of the Fittest," we learn about the Thunderkittens' past before they became street urchins.
Outgrown Such Silly Superstitions: Most of Thundera's opinion about technology, which is fundamentally an aspect of their religion. It's dismissed as fairytales for cubs, and Lion-O is seen as immature and crazy for pursuing it. Then the Lizards invade.