The Turtles confront Kavaxas and must prevent him from destroying the world.
- Back for the Dead:
- Tatsu returns as one of the unleashed spirits, but is brought down with comparative ease by Casey, Donnie, April and Raphael.
- Shredder decides near the end of the episode that he doesn't belong in the living world, and goes back to the Netherworld, after just being revived at the end of the previous episode.
- Big "YES!": Both Tiger Claw and Kavaxas give these during the episode. Tiger Claw give two of these upon Shredder being revived, and Kavaxas gives one of his own when the Seal of the Ancients is shattered and Kavaxas is ready to bring on the apocalypse.
- Big "NO!": Kavaxas gives off a short but loud no when he sees Mikey try to reassemble the Seal of the Ancients, just before Mikey succeeds in rebuilding it and taking control of Kavaxas.
- Body Horror: The revived Shredder is a twisted wreck, with worms wriggling out of his shattered body. Tiger Claw and the other Foot are initially horrified at the sight.
- Brainwashed and Crazy:
- The cultists turn out to be citizens mutated by Shredder's mutated blood into worshipping him.
- Both Rahzar and Shredder himself battle under Kavaxas' command once he makes his play for power.
- Breaking the Fellowship: Shredder's Foot Clan has more or less been severed beyond repair. Fishface, Bebop, and Rocksteady all flee when things get way too weird for them to handle, Shredder accepts his permanent death by returning to the Netherworld, Rahzar is MIA, and Tiger Claw calls a truce with the Turtles.
- The Bus Came Back: One of the spirits unleashed on New York is Ho Chan, the sorcerer from "A Chinatown Ghost Story". He is seen fighting the Turtles and then having to fight a ghost Splinter.
- Came Back Strong: When Shredder is resurrected he is basically a Lich in all but name. He looks like one, and has the ability to levitate the turtles without even touching them.
- He's also capable of controlling severed limbs, and reattaching them including his head.
- Came Back Wrong: How Tiger Claw and the Foot inner circle view the revived Shredder, who is little more than a shambling corpse. Tiger Claw suspects that Shredder hasn't really been revived, and that Kavaxas is simply using him as a puppet. It's clear that Shredder does retain some bit of autonomy, as evidenced by his final actions returning to the Netherworld. Rahzar, meanwhile, is outright referred by Kavaxas as his "undead minion", suggesting his resurrection at Kaxavas' hands gave Kavaxas control over him whenever he deemed fit.
- The Cavalry: When things are looking at their darkest and April, Casey, Donnie and Raphael are beginning to feel overwhelmed by the emerging spirits, Splinter's ghost arrives to handle Ho Chan.
- The Chains of Commanding: Leonardo is feeling the weight of leadership even more than before, and April seems to be the only one who realises the immense pressure he's under.
- Curb-Stomp Battle: Ho Chan is completely powerless against Splinter, who proceeds to smack him around with no effort whatsoever.
- Demoted to Dragon: Kavaxas uses Shredder as his servant.
- Dying as Yourself: Shredder's last words make it clear that he wasn't happy at being used as an undead puppet.
- Emerging from the Shadows: The undead Shredder pulls this off when the Turtles confront Kavaxas and the Foot again, revealing his skull-like face and Glowing Eyelights of Undeath.
- The End of the World as We Know It: Once more the Turtles are faced with having to prevent this, this time by Kavaxas' hands when Tiger Claw loses the Seal of the Ancients and discovers Kavaxas needed him to help him accomplish three objectives to merging the Netherworld and Earth (those three objectives are Kavaxas killing a strong warrior, with Tatsu being said warrior, reviving an evil warrior, who is Shredder, and having the Seal destroyed).
- Enemy Mine: Tiger Claw fights alongside Leo, Mikey, Karai and Leatherhead against Kavaxas and the brainwashed Shredder and Rahzar. Following the battle, Leatherhead mentions that Tiger Claw declared a truce with the Turtles before leaving.
- Evil Laugh:
- Kavaxas gives off a classic villain's cackle when the Turtles infiltrate his lair and Kavaxas drops in and, along with Bebop, Rocksteady and Rahzar, welcomes and corners them.
- Tatsu's spirit also gives off a good Evil Laugh when he hops out of the Netherworld and lands on a street lamp.
- Evil Versus Oblivion: Tiger Claw has no desire to see Kavaxas destroy the world and is perfectly willing to take him, Shredder, and Rahzar on by himself to stop it.
- Face Death with Dignity: Shredder makes it clear that he feels he no longer belongs in the mortal realm as he punches Kavaxas back into the Netherworld, falling in with him.
- Family-Unfriendly Violence: Leo slices off Shredder's head and one arm, on-screen.
- Fighting Your Friend: Tiger Claw is forced to fight off the mind-controlled Rahzar and ultimately kicks him to his potential doom.
- Glowing Eyelights of Undeath: Shredder possesses green ones.
- Heel–Face Turn: Tiger Claw forms a truce with the Turtles once Kavaxas and Zombie Shredder are defeated.
- Heroic Sacrifice: Surprisingly Shredder, who smashes into Kavaxas and punches him back into the Netherworld and falls in with him.Shredder: "We do not belong here, demon!"
- Losing Your Head: Leo cuts off Shredder's head for the second time. However, it's nothing but an inconvenience, and Shredder manages to reattach it.
- Mass "Oh, Crap!": The Turtles, April, and Casey's exact reaction when they discover from Fishface that Kavaxas has already resurrected Shredder.
- My God, What Have I Done?: Tiger Claw's reaction when Kavaxas begins The End of the World as We Know It, especially since he helped him do it.
- Mythology Gag:
- The creation of the Foot's new army bears similarities to the mutant outbreak arc of the 2003 cartoon. There, DNA from Bishop's artificial aliens leaked into the sewers and began to mutate New York's wildlife and human population.
- When everyone compares Xever's story of how the Shredder cult came to be to one of Mikey's lies, Michelangelo insists that he did meet Megan Fox on that rooftop.
- Not What I Signed on For: Xever decides to desert the Foot, things having gotten way too weird for him, as he joined mostly because he just wanted a job that'd give him the opportunity to fight people. Bebop and Rocksteady, meanwhile, were pressed into service by the now deceased Shredder, and flee once they realize they're in over their heads.
- Put on a Bus: This episode features the final appearances of most of the Foot Clan, including Tiger Claw, Rahzar, Fishface, Kavaxas and the Shredder himself.
- The Real Spoofbusters: Donatello builds the team a set of ghost-fighting equipment similar to the proton pack in order to combat Kavaxas and his hoard of evil spirits spilling out from the Netherworld.
- Rule of Three: Kavaxas reveals he needed three things to bring about the end of the world: destroying a mighty warrior (Tatsu), reviving an evil warrior (Shredder) and destroying the Seal of the Ancients (which Shredder does at Kavaxas' bidding).
- Screw This, I'm Outta Here:
- Xever decides to abandon the Foot after seeing the shambling monstrosity Shredder has become. He provides the Turtles with valuable information on what they're dealing with, then flees, only wanting to go back to his old criminal life before all this happened.
- Bebop and Rocksteady realize they're in way over their heads when Kavaxas summons his army of spirits and escape while Tiger Claw and the Turtles battle Kavaxas, Shredder and Rahzar.
- He doesn't actually do it, but before being mind controlled by Kavaxas you can tell Rahzar wants to do so when he sees what Shredder has become.
- Ship Tease: At the beginning of the episode, Rocksteady is cradling Bebop as if to protect him from the revived Shredder.
- Shout-Out: The Turtles don ghost-zapping equipment that make them resemble the Ghostbusters. In particular, the atmosphere and visuals of Kavaxas' apocalypse strongly resemble the climax of the 2016 reboot. Kavaxas's line about a "throne of bone" is similar to Vigo's about "a throne of blood".
- Mikey claims he really did meet Megan Fox on a rooftop.
- This Cannot Be!: Kavaxas basically says this when Mikey repairs the seal with chewing gum.Kavaxas: Impossible! The seal cannot be fixed! How... how is it workiiiing?Mikey: Cause I'm super dope like that, fool.
- Tiger Versus Dragon: A literal example. Tiger Claw, the tiger, helps take on Kavaxas, the demodragon, to stop him from destroying the world.
- Unexplained Recovery: Mikey was pretty beat up at the end of the previous episode (which clearly happens at most a few hours before this one), and yet is fully ready for action.
- Villainous Valor: Tiger Claw was willing to take on Kavaxas, Rahzar and Shredder single-handed to stop Kavaxas' plan.
- What Happened to the Mouse?: We don't see Rahzar again after he falls down the ledge.
- Year Inside, Hour Outside: Shredder describes the time he spent in the Netherworld as "eons," but on Earth, it's only been at least one or two years since his demise.
- You Can't Kill What's Already Dead: Leo slices off Shredder's arm and head; within seconds, he reattaches them both.
- Zombie Gait: The revived Shredder walks with one.
