The Turtles and Casey have gone to an abandoned suburb to train, but quickly discover they're not alone. As the darkness closes in, The Rat King starts to play a very twisted game with our heroes...
This episode provides examples of
- Adaptational Badass: The Rat King. In his first comic appearance, he didn't have any major fighting skills; he relied on vantage points. This version is the Slayer from last season—a Super-Soldier that can take on all five heroes at once and survive all kinds of punishment.
- Adaptational Villainy: In his first comic appearance, the Rat King only menaced the Turtles and Casey because he sincerely believed they were other monsters trying to take his territory from him. Also, he only fed dead or dying animals to his rats before the heroes came along, whereas this episode implies he's been feeding them humans for some time.
- Ax-Crazy: The Rat King.
- Badass Boast: "They fled by now, but I will haunt their nightmares for many days to come. I am the monster they will never escape! Everything fears me! Everything except... the rat."
- Bandaged Face: The Rat King.
- Batman Gambit: Faced with multiple foes, the Rat King runs. He gets them pursue him into a massive feeding area for his little friends.
- The Beastmaster: The Rat King uses hordes of rats to attack the Turtles and Casey.
- Broken Ace: Raph eventually intuits that Leo's insistence on fighting the Rat King is actually him trying to fight a different "monster".
- But for Me, It Was Tuesday: Leo finds the Rat King's moves familiar, but without proper context, he can't tell from where.
- Canon Character All Along: The Rat King is, in fact, the Slayer from the previous season.
- Clone Degeneration: The Rat King.
- Flashback: The Rat King repeatedly experiences flashes of his creation and prior encounter with the Turtles.
- I Am a Monster: The Rat King asserts this in his opening monologue and is proud of it.
- Mythology Gag: Since the episode itself adapts the Rat King's first appearance, his monologues are lifted pretty much wholesale from that issue.
- Nightmare Fuel Station Attendant: In his final monologue, the Rat King expresses certainty he'll haunt his foes' nightmares for many days to come.
- Not Quite Dead: The Rat King is presumably devoured by his rats, but the ending reveals he's still alive.
- Number Two: This is a pretty strong Raph episode. As Leo becomes increasingly preoccupied with fighting the Rat King, Raph takes over leading the remaining team while also keeping an eye on Leo. Raph finds an escape route from the rat attack, answers the others' concerns about Leo fighting the Rat King alone, intuits that Leo needs to fight him alone, indicates he'll be the first to jump in if Leo gets into serious trouble, and eventually manages to break Leo's fugue state enough to get them all out of there safely. It really shows his Character Development that he was able to keep calm and keep everyone safe, even with Leo literally running into danger.
- Oh, Crap!:
- The Rat King when he looks at a shuriken and remembers facing the Turtles before.
- Raph's reaction when everyone else is trying to retreat, only to spot Leo running towards the Rat King.
- Rage Breaking Point: Leo's anger this season comes out, as he has enough of the Rat King and fights him one on one."WHAT'S WRONG WITH YOU?!"
- Rank Scales with Asskicking: Leo's the only one of the group who can face the Rat King one on one.
- Save the Villain: During their fight, Leo tries to push the Rat King out of the way of a building collapse.
- Shout-Out:
- The name of the episode comes from the title of the Rat King's first appearance in the Mirage comics, but that title was a reference to Isaac Asimov's novel, I, Robot.
- As Mikey runs to hide, he whoops like The Three Stooges.
- When Casey just misses seeing him in a dark room, Mikey quips "You don't know the power of the Dark Side, Casey Jones!"
- Suddenly Voiced: In his first appearance as the Slayer in "Bishop's Gambit", the Rat King didn't speak. Here, he speaks in the Cold Open and at the end of the episode. He also laughs and lets out a Big "NO!" at one point.
- Swarm of Rats: the Rat King repeatedly tries to take down the Turtles by using hundreds of hungry rats.
- Taking You with Me: The Rat King tries to drag Leo down to the rats with him.
- Tempting Fate: Casey notes they're just rats and asks how bad they could be. Mikey points to the bones lying on the ground.
- The Unreveal: Inverted. To the characters, the Rat King is practically a Diabolus ex Nihilo, and they're left with only questions about this adventure. The audience, however, quickly learns he is Bishop's lost super soldier.
- Unstoppable Rage: Leo continues to pursue and fight the Rat King, even when the rest of the team is trying to retreat, only finally stopping when a) he's clearly won (but hasn't killed the Rat King), and b) when Raph shouts at him.
- You Dirty Rat!: Whilst Master Splinter normally subverts this trope, this episode plays it very straight with the rat hordes, even giving the rats evil red eyes.
