Anti-Fairy World Pet Store is a place where evil pets live. It is also the home of Anti-Sparky and the Grim Reaper.
When Foop wanted to make Timmy and his parents miserable, he decided to head into the Anti-Fairy World Pet Store to find the Anti-Fairy counterpart of Sparky, "Anti-Sparky".
Unlike what happened to Timmy and Sparky in Fairly OddPet, Foop and Anti-Sparky didn't get along that much but Anti-Sparky decided to agree to switch with Sparky anyways.
So Foop switched Sparky with Anti-Sparky by letting Sparky chase a ball around the world and then let Anti-Sparky cause chaos around the Turner family.
The plan worked so the Anti-Fairy Council decided to order Foop into replace all of the pets in Dimmsdale with all of the evil pets in the Anti-Fairy World Pet Store and let them 'cause chaos around the city.
Fortunately, the plan failed when Timmy, his fairies, and Mr. Crocker freed all of the Dimmsdale pets.