During a school trip touring through a robot factory, Gretel's friend Kelly, often bullied for her clumsiness, accidentally spills a vial full of nanobots. One rogue nanobot then slips into her cast, gradually taking over Kelly and turning her into a mad cyborg as he keeps multiplying.
Tropes:
- Adults Are Useless: Neither Ms. Jamanpour nor Dr. Ben do anything about Kelly being bullied right in front of them. Instead Dr. Ben just marvels at Tucker's advanced vocabulary.
- The Bully: Tucker tends to make fun of Kelly for being clumsy, having several of his classmates join in and chorusing "Clumsy Kelly". When Gretel steps in to defend Kelly, Tucker initiates chorusing "Gregarious Gretel".
- Continuity Cavalcade: Turns out Hamster, Gretel, Kevin and Fred keep the gadgets of all the villains they've fought as souvenirs in Fred's closet, which finally got so full that they have to purge some of it. These keepsakes include the head of an Exclamation Bot, Coach Haggerty's mind-control whistle and smoke bomb pom pom, part of the Onion Amplifier, CopyCat's hairball gun, Gretel's disco ball disguise, the Nightmarionette's staff, Tina's Bolgylvanian arm weapon, a Scorching Chives game cartridge, Tchotchke Jones's mask and shrink-o-bottle ray, and a vat of invisible ink, among others. The issue is resolved by shrinking everything with the shrink-o-bottle ray.
- Exploding Closet: Fred talks about how Kevin is using her spare closet to keep Hamster and Gretel's battle mementos, then opens the closet to show how there's no more room for them, as all the stuff comes falling out.
- Grey Goo: After Kelly spilled the nanobots, one of the scientists points out that there's one missing and talks about how bad it would be if they would be able to reproduce themselves. Which is exactly what happens, as the nanobot, who calls himself Simon, takes over Kelly's cast and builds more nanobots, eventually turning Kelly into a cyborg under Simon's control.
- Injured Limb Episode: Throughout the entire episode, Kelly's right arm is in a cast. This is also the first thing that got mechanized, as well as getting bigger and bigger, since the nanobot hid in there.
- The Klutz: Kelly, to the point she's being bullied for it.
- Sesquipedalian Loquaciousness: Tucker can be surprisingly verbose. This is due to him being part of an after-school program "Bullies Can Talk Good Too!"
- That Man Is Dead: When Gretel tries to talk down cyborg Kelly, Kelly says "there's no Kelly anymore, just Simon." Later, Kelly says that some guy named Simon (the nanobot) was controlling her.
