It's based off the dodo BIRD.
Dodrio is based off of an ostrich.
I heard it was very broken in PMD1, so they changed it.
What do you mean broken?
Goldeen and Seaking, Pokémon that nobody uses, cares about or trains to level 39 (when Seaking learned Waterfall).
Goldeen is awesome, given the right moves. (Ex. Aqua Tail bred)
Mantine is the heaviest Pokemon that you can CATCH in the G/S/C Johto region.