Also introduced baby versions of pokemon which was a huge step in pokemon.
That is literally the most useless mechanic introduced to Pokemon.
On topic: ...can't think of any.
Leveling up a pokemon to evolve it is one of the more enjoyable parts of Pokemon, and creating baby pokemon allows trainers to experience that with pokemon like Electabuzz and Jynx. It's a dumb idea for pokemon like Jigglypuff though, because it already evolves. --- Not changing this sig until we get a new main series Tales game released on a Nintendo console in the US