Largest Ever Pet Shop is an evil, vicious, and malevolent place where pets don't get to hang out with each other, the treats are flavorless and the squeaker toys don't squeak. It's owned by Fisher Biskit. The inside is similar to a prison for all the pets, and Fisher Biskit doesn't seem to care about the pets that live inside of the building. It is the only rival of Littlest Pet Shop. By many fans, it is possibly revealed that this shop contains a chemical that turns pets into monsters under Fisher's control.
In Gailbreak!, it was believed that Zoe's sister, Gail Trent, was put into the Largest Ever Pet Shop by mistake and they went to save her, only to discover it was another dog named Tootsie.
In Terriers and Tiaras it was mention when the producer of Terriers and Tiaras got a call from the Biskit Twins that the Pet Shop has talented pets.