Timmy Turner and his godfamily have come to Fairy World to buy diapers for Cosmo, only to be accosted by Fairy Hart and the Fairy News Network, who are interested in Poof, the only known fairy baby in existence. However, the constant flashes of the cameras disturb Poof. Wanda tries warning everyone that when her son cries, bad things happen. However, the media doesn't take her seriously. Only one closeup flash makes Poof cry, causing a giant camera to appear above them, which snaps a flash and blows all the reporters away.
Meanwhile, in Anti-Fairy World, Anti-Cosmo is bothered by the fact that there is no Anti-Poof, as there is suppose to be an Anti-Fairy for every fairy, there is even an Anti-Jorgen. He is ignorant of Anti-Wanda's wild constant cravings, each anything around her before her stomach begins to expand and bounce her around. When she lands on Anti-Cosmo, he then realizes that there will be an Anti-Poof. Anti-Wanda then begins to expand, before a huge puff of smoke explodes from their castle. This evil cloud rolls towards Fairy World. Wanda's motherly instincts detect this "disturbance" in the Fairy Force, before the cloud engulfs Fairy World.
Once the cloud subsides, Anti-Cosmo sees his Anti-Fairy baby: cube shaped body in contrast to Poof's round body, the standard black bat wings and black crown, purple colored eyes, a black moustache and goatee and an adult voice. Anti-Cosmo decides he name him Foop, though it didn't sound as evil as thought it was in his head. However, Foop is angry that he's not the only fairy baby in existence and decides to destroy Poof. However, Anti-Cosmo tells him that he will do no such thing. He states that they will eventually conquer Fairy World and the universe, but they will do so as a family. However, Foop desires to go solo and zaps his father; Anti-Cosmo says he needs a nap, though Foop yells he doesn't, though he yawns. He then absorbs the magic of Anti-Fairy World's biggest wand to turn the place into a happy land and all the Anti-Fairies into cute, stuffed animals, causing the Anti-Fairies to cry.
In Fairy World, as the Fairies recover, Jorgen Von Strangle turns up, with a fake smile. He asks Timmy and his godfamily to keep quiet about the arrival of Foop. Unfortunately, Cosmo accidentally repeats his words out loud, which Fairy Mary hears and tells everyone to panic. Jorgen tells Timmy and co. to prepare Poof for a fight; Wanda refuses to let her son do so. Timmy attempts to assert that Foop can't be that powerful. He is soon proven wrong when Foop uses his vehicle (reminiscent of Darth Vader's TIE fighter from Star Wars), blows off the Fairy World sign. Timmy and godfamily poof to Earth, while Jorgen held off Foop. Unfortunately, when he refused to disclose Poof's whereabouts, Fairy Mary answers for him. Foop then absorbs all the magic and colour off Fairy World and the fairies and leave them depressed with rain clouds over their heads. He then heads to Earth to find Poof. But before that, he stops to destroy the fast food restaurant planet Burger World when he learns that they are selling Poof toys with their meals.
On Earth, Timmy begins boarding up his room, as Poof begins to weld something before sleeping. Unfortunately, Cosmo uses up the reserve magic in both his and Wanda's wands. Worse, Foop arrives and unleashing the worst plagues on Dimmsdale: paper cuts, spiders, pinkeye and crazy cow disease. He then rips the roof off Timmy's house and then conjured up a spider-cow to grab both Timmy and Cosmo before blasting Wanda aside. Luckily, Poof had woken up and blasts Foop through the wall before pulling a wedgie on him. He then takes off in his X-Wing-like vehicle, followed by Foop. Foop conjures up the Ballpit of Doom, the Teeter-totter of Terror and the Merry-go-Round of Mayhem. However, all this is slowly making him tired, which Poof takes advantage of, by doing everything possible to make Foop sleep. Timmy also notices this as well. He frees himself from the spider-cow and uses a camera to call out to all fairies, Anti-Fairies and Burger World employees to come to Earth and sing a lullaby to lull Foop to sleep. This works, just as Foop had Poof at his mercy. Both fairy babies then fall into their respective mothers' arms.
Though Foop is beaten, they still need a way to fix all the damage he had done. Timmy figures that since Foop is the opposite of Poof, then his crying would make good things happen. Poof ensures this by taking away Foop's bottle from him (He protests "YOU TOOK MY BUBBA?"). His cries then reverse all the damages he had done. Foop is then locked in Abracatraz. However, his parents sneak in a nail file in his birthday cake. He swears to get out one day and destroy Poof once again. However, Poof is then revealed to have Foop's magic bottle with him. The episode ends with Mr. Crocker chase the cow while saying "Who's the boss now, Buzzy?"