On Friday the 13th, the Anti-Fairies got loose and started wreaking havoc onTimmy Turner's trip to Adrenalland by causing bad luck all over the place. The Anti-Fairies were originally invisible, and could only be seen with a device that, when Timmy put on, he saw and met Anti-Cosmo. Being Cosmo's opposite, Anti-Cosmo was extremely intelligent and was respected as their leader who sarcastically congratulated Timmy for freeing them.
In his next appearance, Cosmo's Fagiggly Gland goes bad and he needs a replacement, and the only match is Anti-Cosmo, who escapes from captivity shortly after the transplant. Anti-Cosmo told Cosmo to not look for him, but Cosmo does not obey and finds Anti-Cosmo behind him. Anti-Cosmo then realizes part of Cosmo is in him before leaving while Cosmo displays some traits of Anti-Cosmo.
Later Anti-Cosmo tries to frees his captive comerades, but fails due to Jorgen. Later with the help of Calamitous, Anti-Cosmo is able to free the other Anti-Fairies. One half of the group was sent to create so much bad luck while the other half was sent to stop the Earth from rotating to keep it at Friday the 13th. Because there are too many Anti-Fairies to undo the damage done through a wish, Timmy and his friends go to the Crocker Cave and find a butterfly net which should be sufficient on catching the Anti-Fairies. Jimmy combines the net with his hyper cube to create a trap for the Anti-Fairies. Jimmy's friends, Cosmo, Wanda, all create as much bad luck as they can. This lures all of the Anti-Fairies to the exact location, including the ones that were keeping the Earth from rotating. Jimmy then activates his hyper cube which captures all of the Anti-Fairies and traps them inside the hyper cube. It is unknown what happened to the hyper cube, but Jorgen most likely took it with him, so he could trap the Anti-Fairies back in their imprisonment again.
After he and the bulk of his race escaped from Fairy World's jail, most of the Anti-Fairies took up residence in Anti-Fairy World to plot their next move against Fairy World and Earth. After the first fairy baby in eons was born to Cosmo and Wanda, Anti-Cosmo plotted with the Pixies in an attempt to steal the young baby Poofbefore his magic could be controlled by the Fairies. They did not succeed and Anti-Cosmo and HP ended up being raisins for Jorgen's cereal temporarily due to Poof breaking wind on them.
Later Anti-Cosmo demands equality and is not happy that fairies are appreciated for things they create when Anti-Fairies have created things too. Anti-Cosmo then begins to question why there is no Anti-Fairy for Poof since there is supposed to be an Anti-Fairy for every fairy. He then notices the symptoms that Anti-Wanda had for anti-fairy pregnancy. Anti-Wanda then gave birth to Poof's Anti-Fairy equivalent, Foop, who is even more evil and untrustworthy than Anti-Cosmo. Foop betrays his race and turns Anti-Fairy World into a cute and cuddly place, much to its residents's horror. Despite this, after Foop was captured, the damage he did was reversed when Poof made him cry. He was then taken away to Abracatraz where he would be held for rehabilitation. Anti-Cosmo and Anti-Wanda then paid him a visit, hoping to slip him some tools to escape. Although Foop eventually did manage to escape, it was by his own devices and not with the help of his parents.