Foop is born to Anti-Cosmo and Anti-Wanda, yet quickly learns that his Fairy counterpart and nemesis, Poof, has already stolen the thunder of being the first fairy baby born in centuries. After turning on his parents and the Anti-Fairies, Foop sets his sights on destroying Fairy World, and then Earth. He is eventually stopped by Poof who uses a lullaby to put him to sleep, and Foop is brought to Abracatraz and placed in a solitary confinement playpen.
Using a recording of Jorgen Von Strangle, Foop calls Wanda and tricks her into setting up a playdate between him and Poof. After escaping Abracatraz, Foop arrives at the Turner household a "reformed" Anti-Fairy, but his real intent is made clear to Poof. By tricking Wanda and Cosmo into thinking Poof is picking on him, Foop hopes that Poof will be placed in a timeout playpen he brought with him as a "present", but it is actually a portal to outer space. Timmy Turner catches Foop in the act several times, but he is whisked away by his parents before he can tell Cosmo and Wanda about Foop's plan. Foop nearly succeeds and Poof is nearly sucked into outer space, but Timmy interferes and causes Foop to get sucked into the portal instead. While floating through space, Foop argues with himself (having developed schizophrenia while in solitary confinement) and vows his revenge.
It is the first day of Spellementary School for both Foop and Poof. Foop strives to be the most popular student among his classmates, and to win the class presidency, but he is beaten by Poof at every turn. Foop turns on his class instead and coverts the school into a twisted evil lair. Poof attempts to rescue them by battling Foop in a Star Wars lightsaber battle, but fails, and Foop nearly succeeds in destroying Poof until the school bell rings, causing all the magical changes made to the school to suddenly revert. Foop earns nothing except for a detention, although he is pardoned by Poof, much to his annoyance. While leaving school, Cosmo sees a sprite on Foop's nose and hits him with a shovel repeatedly, trying to swat it, as the episode ends.
Foop and Poof are slowly becoming friends, mainly because of their shared disdain for going to school, but their friendship disintegrates when a new girl arrives at school named Goldie Goldenglow, a fairy baby who is shaped like a golden triangle. Poof and Foop fight for Goldie's affections, and when they learn she is in the Mr. Cookie school play as the lead girl, they each seek the role of Mr. Cookie, which Poof wins. Foop whines until he is made Poof's understudy, allowing him to take the role of Mr. Cookie should Poof not show up. Foop attempts to injure and sicken Poof, but fails and only causes harm to himself. Foop decides to kidnap his teacher Mrs. Powers and then force his class into a new play instead where Mr. Cookie and Table Number #3 (Foop's role) swap roles. Poof sees this and fakes sickness, forcing Foop to take up the role of Mr. Cookie, which he obliges until he realizes his new play script causes great harm to Mr. Cookie. Foop is beaten and battered around the stage, humiliated, and then eventually rescued by Poof after a monster he summoned goes out of control. Foop is then taken away by Mrs. Powers and given detention. Later, while Poof and Goldie were sharing an ice cream, Foop attempts to bomb their table, but ends up blowing himself up.
Foop becomes Vicky's anti-fairy godparent, and together, they terrorize the children of Dimmsdale. However, Foop gets tired and of Vicky when she goes too far with her wishes, such as forcing him to wear sandpaper diaper. Thanks to Timmy persuading he turns against her.
Foop is disgusted with Turner family's happiness, and all because of Sparky. So has an idea to replace Sparky with an evil creature from the Anti-Fairy World Pet Store. Inside the store he notices Anti-Sparky. He is delighted that the Anti-Sparky is so horryfing. On Earth, Foop explains to the anti-dog what has to do, but Anti-Sparky explains him the rules he need to follow. Foop is downright scared and constantly bullied by him. However, the plan worked and the Turners are miserable because of the Anti-Sparky. Suddenly Foop and Anti-Sparky are transported to the Anti-Fairy Council who tell him that they were impressed by his actions and tell him that he must replace all the animals in Dimmsdale with these from Anti-Fairy Pet Store. When Timmy and his fairies discover the truth, Foop shoots at Wanda and Cosmo from his bottle and Anti-Sparky devours their wands. When the Anti-Sparky is again yelling at Foop he has had enough of his threats and puts himself to him. In retaliation, the anti-dog eats a small anti-fairy baby. At the end, Foop is spit out from the interior of Anti-Sparky. He is furious that Timmy hindered him in his an evil plan and is about to destroy him, but at this point Anti-Fairy Council appears, telling him that he didn't make the task and will be taken back to the Anti-Fairy World.