Last year some differences were leaked in what the original appearance looked like and how it ended up being the final appearance of some Pokémon of the 4th generation of Pokémon Diamond and Pokémon Pearl.

Here are some images where the 2 versions are compared, the initial and the final.

List of Pokémon offered by Dr. Lava:

Monferno

Wormadam

Gastrodon

Magmortar

How did you find these differences?

Via.