
Jimmy McGarfield (the fourth-grade president) forces other kids back into school on a first snow day for a special assembly after Numbuh One is too sick to play. Soon Mandy becomes ruler of the KND, renaming it the MND (Mandy New Dicta Only Numbuh 5 and later, Numbuh 362 knew that she's an impostor, but since nobody else does, Mandy convinces everyone that Numbuh 5 is losing her mind. Sector V returns to the Moonbase, where they find Mandy disguised as Numbuh 1. The Delightful Reaper begins fusing kids into it, including Numbuh 2. In a sudden show of pain, Grim senses that his scythe has been fused with evil and strangely delightful children, and Numbuh 1 realizes that he is talking about the Delightful Children from Down the Lane. Meanwhile, Grim comes to Billy's house, and mistakes Numbuh 1 for Billy. Sector V reluctantly takes Billy on the mission, where he mistakes the delightful machine for a bathroom, fusing him, the lucky pants, Grim's scythe and the Delightful Children (who only ran inside the machine to pull Billy out) into a being called the "Delightful Reaper". Meanwhile, the rest of Sector V are flying Billy to the Deep Sea Base, and they get an urgent message that the Delightful Children from Down the Lane are using a "delightfulization machine" to make more children into their delightful slaves.

Mandy captures Numbuh 1, and tortures him until Numbuh 1 tells Mandy everything about the KND. Mandy comes to Billy's house, and knows that Numbuh 1 is not Billy. The KND soon arrive (Billy is confused by this, stating that he tried to call the Power Puff Girls"), and they find they need 2x4 Technology, so Numbuh 1 dresses up as Billy to stall Billy's dad, while the rest of Sector V take Billy to the KND Deep Sea Base to fix the pants. He calls "Ed, Edd, n Eddy's Pesky Problem Fixers", but Billy doesn't have any money, so Eddy tells him to call the Kids Next Door since "they're cheap." Billy accidentally gets Grim's scythe stuck in the pants, and he tries to get help fixing them before his dad gets home. When Billy's dad leaves to buy underwear, Billy wears his dad's "lucky pants", despite being told not to.
