This Vulpix is a Fire-type Pokémon owned by Suzy, which was given to Brock for a while.
Through seeing the care that Brock went into in looking after Pokémon, Suzy decided to let Brock look after it. Brock was often seen grooming it and sometimes used it in battle, mostly however in training with Ash. Vulpix, while a little bit spoiled, did enjoy playing about with the other Pokémon. Eventually Brock met up with Suzy again and decided that Suzy should keep Vulpix at the Pokémon Beauty Show.