>>49301688GameFreak basically had no concrete designs and consistency to worry about up until Yellow thanks to the anime requiring proper designs to go off of. Prior to that they were doing whatever the hell felt right in the moment based on their amateur approach to game development, so it let a lot more curious interpretations and depictions come up like some of the previously posted sprites.
The one that always sticks out to me most, though, it's always been Gastly. It's practically a completely different monster from Sugimori's depiction and its future standard appearance in Yellow onward, one that really captures the "spectral entity made entirely out of gas" look compared to the more familiar Gassy Will-o'-Wisp look.
