My interpretation of MissingNo. 79 from its back sprite.
This beta Pokémon was apparently based on a flying fish/betta fish mixed with some more bird-like appearance. It was probably meant to be a Water/Fighting Pokémon, featuring both fins and feet.
The little pink menace. An absolute icon for growing up with. I loved that the 'girly' creature trope was given such a funny and unstoppable role in the series! She stays uncaught and is a problem always. Inspiring!