Welcome to Pokemon ramble, where i talk about something quite simple and easy to understand and i tell you nothing more, just making it kinda complicated.
This time, i will talk about Chansey’s evolution line and the generations of release.
So most pokemon got pre-evolutions in Generation 2, but Chansey got an evolution. Now gaining evolutions was not only for Chansey, because other pokemon got evolutions. But those pokemon didnt get pre-evolutions in later gens.
In Generation 4, lots of pokemon gained evolutions, but Chansey got a pre-evolution, some other pokemon gained pre-evolutions but those Pokémon didn’t have evolutions given to them.
So now you might see what i mean by evolving backwards: Happiny and Blissey swapped Generations, if you look at it with this logic
Just thought it was something to tell you.