While the Planeteers are watching the launch of an exploring robot, JASON, being tested in the Galapagos Islands, they catch sight of an unwelcome surprise: Greedly and Skumm, who have gotten shipwrecked there and are currently wreaking havoc on the local tortoise population.
This episode includes examples of the following tropes:
- Accidental Hero: Downplayed; Wheeler feeds Skumm's rats the leftover pizza as a distraction to keep them from mauling the Planeteers. However, then it turns out that eating normal food reverses the effects of the toxic waste, returning the rats to normal size and making them much less of a threat.
- Attack of the 50-Foot Whatever: Greedly and Skumm end up in the Galapagos and begin gathering turtle eggs. While cooking, Greedly drops some of them in a toxic waste barrel that Skumm brought. When Greedly trips while carrying toxic-waste-soaked eggs, he grows into a gargantuan monster version of himself.
- Brief Accent Imitation: While they're walking through a museum exhibit, Wheeler briefly puts on an Australian accent and uses some Aussie slang while flirting with Linka.
- Chekhov's Gag: Wheeler ordering pizza is just played as a joke and a sign about how out-of-touch he is, but when the Planeteers are cornered by Skumm's giant rats, Wheeler manages to reach the Geo-Cruiser and pull out the pizza. The rats are happy to eat that and leave the currently powerless team alone.
- Cower Power: When the rats mutate and grow huge thanks to toxic waste exposure, Greedly hides behind Skumm and tells him that he should deal with them; they're his relatives.
- Devoured by the Horde: Skumm is initially able to get the enlarged rats to back off, but Greedly worries that if they can't reach somewhere with food soon, the rats will eat them instead. Skumm also seems to have this in mind when he sics them on the Planeteers. However, once Wheeler begins throwing them pizza, they're quite content to take the easy meal rather than continuing to fight the humans.
- Improbable Antidote: The size-enhancing toxic waste wears off in a minute or so after the being exposed to it eats something normal (in the rats' case, Wheeler's leftover pizza).
- Introduced Species Calamity: The Aesop of the week is not to bring new animals into different ecosystems, with cane toads being cited as an example. Once Captain Planet has gotten Skumm out of the way, Ma-Ti gathers the rats into a cage for transport away from the islands so they can't eat the turtle eggs.
- Lost My Appetite: Wheeler is snacking on some pizza when Gaia (via Planet-vision) shows him the effects of non-local animals on environments. He puts the pizza down and tells Linka that he thinks he lost his appetite.
- Jump Scare: While Wheeler is flirting with Linka, she advises him to look where he's going. When he does, he comes face-to-face with a Tasmanian Tiger, causing a yelp. It's Ma-Ti, playing a prank with one of the exhibits.
- Mama Bear: Shelley stands over her nest and snaps at Skumm's giant rats as they try to steal her eggs.
- No Honor Among Thieves: Skumm and Greedly team up for this episode, but when their attention isn't focused on the heroes, they're just as likely to harass each other. Greedly retroactively labels the turtle eggs that fell in the toxic waste Skumm's breakfast and Skumm, who comes up behind, retorts that he'll throw Greedly into it. Their ensuing name-calling (and maybe physical fighting) only stops because the Planeteers arrive just then. Both of them try to run off and leave the other on separate occasions when the fight goes against them. Finally, Greedly attempts to catch and eat Skumm to restore his normal size after they're stranded on a bare rock.
- Pop-Culture Pun Episode Title: The episode's name refers to the title attributed to Michaelangelo, Raphael, Leonardo and Donatello: "Heroes on the Half-Shell".
- Punny Name: Sean, JASON's pilot, names one of the local turtles "Shelley."
- Rodents of Unusual Size: Skumm's toxic sewer waste causes anything exposed to it to grow. Skumm's rats become the size of large dogs after Greedly splashes them with it.
- Sapient Eat Sapient: Implied; Captain Planet dumps Skumm and the now-gigantic Greedly on a bare rock while he and the Planeteers clean up the mess they made. The episode ends with Greedly chasing Skumm around as the rat-man tries to dissuade him. Skumm reminds him that eating something normal can return him to regular size, and Greedly demands what Skumm thinks he's trying to do.
- Shout-Out: The episode is full of references to Teenage Mutant Ninja Turtles.Linka: How can you think about pizza with what is happening to those turtles!?Wheeler: I don't know. Turtles, pizza, must be something subliminal.
- Smooch of Victory: Linka pecks Wheeler on the cheek after he saves the others from the rats using leftover pizza and accidentally changes the gigantic rampaging rodents back to normal.
- Swarm of Rats: Skumm, naturally, brings a group of regular rats with him wherever he and Greedly are going. They grow huge from exposure to the toxic waste and serve as Skumm's minions. However, once Skumm is out of the picture, Ma-Ti is able to command them into a box for transport off the island easily.
- Toxic Waste Can Do Anything: The Captain notes that on TV, toxic waste tends to make you super-powerful, but unfortunately, it's different in real life. This is undercut by the fact that the episode uses the trope straight; Greedly and Skumm's rats both grow huge because of the toxic waste.
- Wounded Hero, Weaker Helper: Captain Planet, downed by poisoned eggs, has to be dragged to the ocean by JASON and one of the local turtles (who JASON's pilot Sean names Shelley).
