Arnold lives with his mother in Hophophop Town, a large city where the Pokémon Fan Club was using their Hypno and Drowzee to help their members get to sleep. The members of the Pokémon Fan Club were unaware that it was causing side effects with the children in the town including
Arnold.
Arnold's Mother was searching for
Arnold after he went missing and mistook
Ash Ketchum for
Arnold because according to her,
Ash Ketchum just looked like her son.
Ash Ketchum and his friends decided to help out
Arnold's Mother and try to find out where
Arnold had disappeared to. After
Ash Ketchum and his friends with the help of
Officer Jenny tracked down the kids to a park in the middle of Hophophop Town,
Arnold's Mother randomly showed up in the park and was reunited with her son.