Donatello is sick so he is staying with Casey and April. However, he starts turning into one of the mutants that the Turtles will have to fight against.
This episode provides examples of
- Accidental Pun: April notes that Don is looking green before realizing that this statement needs some more clarification.April: Whoa. Don, you look greener than usual. A lot greener than usual.
- Actually, I Am Him: Leo, Raph and Mike attack Monster Don at April's basement then wonder what happened to Don.Leo: What was that thing?
Raph: And where's Don?
Mike: Did that monster get Don?
April: Guys, that monster is Don!
Mike: Say what?
April: That thing you just fought is Don. - Art and Vocal Evolution: Leatherhead not only has lighter skin than before, but he now has a more pronounced accent.
- As You Know: Leatherhead uses the exact words when explaining how he and Don made the containment unit. Since this is Leatherhead's first appearance this season, it's meant to be exposition for the audience.
- Back from the Dead: Baxter Stockman, thanks to Bishop saving his brain and attaching it to a new cyborg body.
- The Bait: Mikey gets volunteered by the others to lure mutated Donnie towards the containment cell where he can be held until they figure out how to help him. Mikey is not excited about this.
- Big Brother Instinct: Both Casey and April are a bit annoyed, Casey even more so, when the Turtles ask them to take care for a sick Don, as this means their plans for a romantic evening is ruined, but they both decide to look after him anyway. Casey is the one who tucks Don in and covers him with a blanket.Casey: Come on, sickly mutant ninja turtle, you better lie down before you fall down. (Helps Donatello lie down on the couch and then covers him with a blanket) There. Comfy?
- Big "WHAT?!": Mikey does one of these and a Big "NO!" when Leatherhead says he can't cure Donnie.
- Big "WHY?!": Stockman's reaction to being revived yet again.
- Brainwashed and Crazy: While Donny's not quite brainwashed, he is mutated and certainly crazy enough to live up to the spirit of the trope — unwitting Face–Heel Turn included.
- The Bus Came Back: Leatherhead makes his first appearance since "Exodus".
- Call-Back:
- All the way back to "Outbreak", which is where Don picked up the mutagen in the first place.
- Bishop bringing Stockman back in a new cyborg body is also a reference to "Insane in the Membrane".
- Can't Kill You, Still Need You: Or rather, Can't Let You Die, Still Need You. Even besides Stockman's general usefulness, Bishop really needs his help working on the outbreak virus.
- Chekhov's Gun: The tunnel to April's apartment: introduced in "The Trouble with Augie".
- Continuity Nod:
- Stockman has to be resurrected from the dead after his failing clone body fell into the river and drowned in "Insane in the Membrane". Since that episode never aired during the series' original run, viewers were left confused as to why he had to be resurrected until it released on the "Season 4" DVD.
- This episode features April's basement apartment, which hadn't been seen or referenced since "The King", three seasons earlier. It even had the appropriate pieces of furniture in it, like Kirby's drawing desk.
- In the beginning of the episode, Donatello is sneezing like in "Return of Savanti". This is revealed to be one of the symptoms of his secondary mutation.
- Curse Cut Short:Raph: I'm gonna take Bishop and shove my foot so far-Leo: Easy, Raph!
- Death Seeker: Downplayed. While he's not shown actively trying to kill himself in this episode, Stockman is deeply unhappy to learn he had finally died but is now brought back indefinitely to continue serving Bishop.
- Downer Ending: Donatello is left a mutated, mindless monster that must be kept in a cell. Baxter Stockman is revived. He will spend the rest of the series tortured at being ripped away from the peace death finally granted him.
- He Cleans Up Nicely: Casey in the suit and with his hair done.
- Hulking Out: Don mutates into a Hulking beast, even bigger than the already huge Leatherhead.
- Metamorphosis: Don into a monster.
- Mood Whiplash: The episode starts out like a rather normal mutated monster catching episode with Donnie seemingly just being merely sick at first... then Donnie starts mutating into a monster.
- My Friends... and Zoidberg: Mikey says they need to save Don and April. A very annoyed Leo then reminds him that Casey also needs help.
- Mythology Gag:
- The idea of a Turtle undergoing a secondary mutation into a monstrous form has appeared in other parts of the franchise, including the Fred Wolf series and Mirage's fourth volume. In fact, Don's monstrous mutant form strongly resmbles "Gameraph", Raph's secondary mutation from the Mirage comics.
- The 1987 series also had an episode of the same name.
- Open Mouth, Insert Foot: While facing some mutants at a power plant, Leo briefly forgets that Don is not there with them.Leo: Okay, Mikey, you take the left. Don, you cover me on—
Mike: Uh, Don's home sick from school today, Leo. - Poor Communication Kills: Downplayed in regards to April and Casey going on a date. April dresses up as a Badass Biker because she thought they were going on a romantic motorcycle ride, while Casey arrives at her apartment as a Sharp-Dressed Man under the assumption they were going to dinner together, causing a lot of awkwardness between the two. But they realize the good intentions the other had and have a good laugh.
- Resist the Beast: Donny's transformation into mindless beast is obviously painful, yet he's able to resist it for long enough to beg April and Casey to 'stay away from' him as he runs from the room, only to turn into a monster and start attacking them.
- The Reveal: Donatello had been infected by the mutant outbreak and is now a monster.
- Shapeshifting Excludes Clothing: Donnie's elbow pads, knee pads, and belt visibly tear off his body as he mutates.
- Shout-Out:
- Mikey saying, "Like zoinks!".
- The title is also a reference to Adventures in Babysitting.
- Sick Episode: For Donatello... until it's revealed to be something much worse.
- The Smart Guy: Leatherhead takes up Donnie's role as this in the team.
- Unwanted Revival: Bishop retrieves Stockman's brain and attaches it to a new cyborg body, needing him to work on a cure for the outbreak. Stockman is absolutely mortified that he wasn't left to rest in peace.
- Vomit Discretion Shot: Discussed:Donatello: I just can't handle mutants right now.Michelangelo: Did you figure that out before or after you barfed in the Battleshell?
