Stunfisk is the first Pokémon that has a Ground/Electric-type combination.
Despite living in water and being based on a fish, Stunfisk is not a Water-type.
Before Pokémon Black and White, Stunfisk originally had Electric as a primary type, and Ground as a secondary type, but later it turns to have Ground as its primary type, and Electric as a secondary type.
Stunfisk is the one of the two Electric-type Pokémon to be weak to Water-type moves, Heat Rotom being the other.
Both of Stunfisk's abilities, Static and Limber, are related to the paralysis status condition.
Static has a 30% chance of inflicting the paralysis status if hit by a physical contact move to the attacker, while Limber prevents Stunfisk from being paralyzed.
Stunfisk's name comes from the word "stun", and the word "Hundfisk" which is Swedish for "Mudminnow"
Stunfisk is the only known Pokémon to both be weak against its own type and immune to its own type, as well as being the only aquatic Pokémon to be weak to Water-type moves.
If you talk to a doctor in Humilau City, he will tell you that sleeping on a Stunfisk relaxes the body with its electricity.