The Turtles meet Raptarr, an Avian who's been living on Earth to keep watch over his enemy and former friend, Mephos. When Mephos gains the upper hand, it's up to the Turtles to help Raptarr stop his dark plans.

''First appearance of Raptarr''
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!! This episode provides examples of

* AesopAmnesia: Despite the events of [[Recap/TeenageMutantNinjaTurtles2003S4E6GrudgeMatch the very last episode]], Mikey's back to goofing off while his brothers train. [[LampshadeHanging Leo explicitly calls him out on this]].
* ArtificialLimbs: Mephos' real wings was removed as punishment for rebellion. He now has black — [[RazorWings and very sharp]] — metal wings.
* CallBack:
** Leonardo reprimands Michelangelo for slacking off even after the lesson he learned in "Grudge Match."
** Raptarr reveals that the Avians were servants of the Y'lyntians, who the Turtles met in Season 3 episode "The Entity Below."
* CatchAFallingStar: Raptarr catches Mikey when he topples off the building top. Somewhat explained by the fact that Raptarr has wings to help him catch up to Mikey.
* CombatPragmatist: Mephos will really fight dirty if he sees any weakness, particularly when he targets Raptarr's still-wounded wing.
* ContinuityNod: When Raptarr explains that a Y'lyntian crystal is needed to find the Avian city, Donatello mentions he used up all the crystals that were in their lair when he was working to cure the Turtles' mutated friends. Fortunately, Raptarr reveals there's still a supply of them hidden in the ceiling.
* CripplingTheCompetition: Mephos, an Avian who was punished for crimes against his race by having the wings torn from his back and being forced to live as a human.
* EvilFormerFriend: Mephos to Raptarr
* FantasticRacism:
** The Y'lyntians forced the Avians to live in a floating bird cage due to feeling they "befouled" their city.
** Mephos is constantly referring to residents of the surface by monikors such as insects and apes with a sneer. He even uses the word "befouled" indicating that he is no different from his ancestors slavers.
* FeatherFlechettes: Mephos' cybernetic wings allow him to pull this off.
* HairOfGoldHeartOfGold: Raptarr is a blonde-haired nice guy working hard to protect his people and the surface alike.
* HiddenElfVillage: The Avian city
* JetPack: Donny has invented several which are used to reach the Floating City.
* KeepAway: This is how the Turtles defeat Mephos, by tossing the control crystal to each other, forcing Mephos to chase after them until Mikey gets him close enough to main core to get electrocuted.
* LightIsGood/ DarkIsEvil: Raptarr (the good Avian) is blond with white wings. Mephos (the bad Avian) is black haired with black (metal) wings, and pale grey skin.
* NoodleIncident: Mephos has apparently made several previous attempts to make it back to the city and launch a coup which Raptarr narrowly stopped.
* PerspectiveFlip: The Y'lyntian uprising again is shown, from the Avians POV, giving an emphasis to how they escaped.
* ShoutOut: Mikey ends up butchering [[Franchise/StarWars Yoda's]] "Fear leads to anger" speech from "The Phantom Menace"
* TheRemnant: A short-lived, heroic version when Mephos's crew soon has three Avian counselors and a handful of guards holed up in a tower as the rest of the city government has joined him or been captured. They themselves get captured in short order but Mephos's coup doesn't last long.
* TheReveal: Raptarr helps the Turtles discover that, since their lair is a Y'lyntian outpost, there's a number of crystals in the ceiling.
* WeCanRuleTogether: Mephos makes a half-hearted effort for Raptarr to join him.
* WingedHumanoid: The Avians.
* YoureInsane: Mephos offers to let Raptarr join him, the latter calls him mad for suggesting it.
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