While the Turtles are infiltrating an undersea Kraang base, the Foot Clan attempts to capture April.
This episode provides examples of:
- Bait-and-Switch: The sea monster pursues the Turtle sub like it's going to attack, but it's actually trying to mount it.
- Book Dumb: April mentions she's failing trigonometry.
- Call-Back: Murakami returns after being absent since "I, Monster".
- Can't Catch Up:
- In addition to April's training as a kunoichi averting Instant Expert, her fight with Karai makes no attempt to dodge the hard truth that someone who's been training for years and has been in actual fights is going to beat someone who has never been in a serious fight and has only been training for, at most, a few months.
- Inversely, a skilled and experienced opponent can still lose a fight due to vulnerability and sheer bad luck, April managing to escape by kicking her down a subway staircase in a split-second moment of distraction.
- Chekhov's Classroom: April observes Splinter teaching Raph and Mikey how a captured ninja should do anything to break a foe's concentration in order to escape. Later during the fight, April recalls what he said before taking advantage of Karai's hesitation.
- Compromising Call: As the Turtles sneak into the Kraang base with perfect stealth, that moment gets ruined when April calls them through Donatello's T-Phone to tell him that Karai is after her.
- Cool Bike: Karai owns a sleek red-and-black motorcycle. It appeared for a brief moment in the previous episode but gets a lot more screen time here. It bears more than a passing resemblance to a Kawasaki Ninja.
- Curb-Stomp Battle: She managed to land one lucky hit and take advantage of a momentary distraction to win at the end, but April was no match for Karai.
- Damsel in Distress: The Foot Clan is after April this time but she takes care of it.
- Did I Say That Out Loud: After the turtles have gotten back to the Lair and Donnie is frantically trying to contact April on his T-Phone. Luckily, she picks up and Donnie calls her his "sweet princess", much to his brothers' annoyance.Donnie: Come on, April! Come on, April!April: Hey Donnie!Donnie: April! You're okay! You hear that, guys? My sweet princess is alive! [Beat] Did I mute that?April: Let's agree that you did.
- Facepalm: Leo, Raph, and Mikey had this type of reaction after Donnie calls April his "Sweet Princess".
- Foreshadowing: April is unharmed by the pure Kraang-water that a moment before had completely dissolved a pizza slice.
- Freeze-Frame Bonus:
- Donatello's caller ID on April's phone is labeled "Donny Boy", and his picture is decorated with a bow on his head and with flowers and stars around the border.
- A quick eye will notice Karai's order at Murakami's restaurant before she says what it is: The wooden piece has a Turtle on it.
- From Bad to Worse: Played for laughs. What's worse than your sub being pursued by a sea monster? Finding out the sea monster is in love with the sub. That's crossing the line there.
- Green-Eyed Monster: Karai demands to know what makes April so special while she's pounding her into the dirt.
- Hamster-Wheel Power: The Turtle Sub is equipped with jets for quick action, but to charge them up and for stealth, it also runs on three bicycles that move the flippers. Leo, Raph, and Mikey are the power source for those.
- Hero Stole My Bike: April steals a pizza delivery boy’s bike to try and escape from a pursuing Karai. She promises to return it though.
- Heroic Bystander: Murakami dumps a bowl of soup on Karai and stalls her to help April escape, all while pretending to be a blind klutz.
- Heroic Resolve: No matter how many times Karai beats her senseless or throws her down, April just keeps getting right back up to try again.
- Innocently Insensitive: Donnie's reaction to April having to give up her entire life. (At least temporarily.)
- Jerkass Has a Point:
- When April calls the turtles for help against Karai, Don wants to abort the mission and help her, but Raph points out that foiling the Kraang's water poisoning plans are more important otherwise they'll be endangering everyone in New York including April.
- In Space Heroes, the Captain states that if they keep bailing out their trainees, they'll never learn how to take care of themselves. This falls under Sink or Swim Mentor given the circumstances of those trainees.
- Made of Iron: The Kraang creature survives the explosion of the base with no ill effects.
- Meaningful Name: Karai goes under the fake name Harmony when pretending to befriend April. The name Miwa can mean Harmony.
- Missing Mom: Mentioned by April and it's implied Karai may also fit this trope.
- Mythology Gag: The turtles' masks all look red through the sub's windows.
- Never Trust a Title: Despite the name of the ep it doesn't have a vendetta. Karai yes, Vendetta no.
- No-Holds-Barred Beatdown: A mild version, but Karai lays into April when the two finally fight.
- Oh, Crap!: April when she realizes "Harmony" is really Karai.
- Pet the Dog: Karai genuinely feels sad for April when she learns she has a Missing Mom.
- Skewed Priorities: As soon as they discover that Karai is after April, Donnie is fully prepared to drop their mission and help her. The others get him back on track by reminding him that if they don't stop the Kraang's plans and destroy their base, then the Kraang will poison everyone in New York, including April.
- Staircase Tumble: Karai doesn't so much fall down the subway stairs as get bodily thrown down them by April.
- Stock Ness Monster: The Kraang sea creature guarding the base bears a great resemblance to many illustrations of Nessie and plesiosaurs in general.
- Storming the Castle: The tradition of the Turtles sneaking into Kraang labs continues.
- Stunned Silence: When the sea monster finally catches the T-Sub and is making amorous noises, the turtles sit in silence for a few seconds while wearing shocked expressions.
- Tempting Fate: While in the Kraang's underwater lab, Leo tells the others to be quiet. Don points out there's no need for Leo to say that every time since they're ninjas and they know how to be quiet. Cue Don's T-Phone ringing.
- Underwater Base: The Kraang's base in this episode.
- You Can't Go Home Again: With both the Kraang and the Shredder out to capture her, Splinter and the Turtles decide that April will have to stay in the sewers with them for her own safety, at least until the crisis is resolved.
