Starting with Gardevoir has there been at least one Poke-Waifu in each generation? Or was there some that even pre-date Gardevoir?

Also when and how did the Vaporeon meme come about? I get being horny for something with feminine curves and other features but why a fish-cat creature?

nothing too obvious in gen 1 and 2. Unless you count Jinx? Not too much in the way of humnaoid pokemon in the older generations.

Tetsamaru said:

Not too much in the way of humnaoid pokemon in the older generations.

I doubt that stopped some of the more hardcore parts of the Poke-Furry community. I remember when Sword and Shield was coming out seeing some Wooloo lewds appearing.

Monki said:

I doubt that stopped some of the more hardcore parts of the Poke-Furry community. I remember when Sword and Shield was coming out seeing some Wooloo lewds appearing.

ANY pokemon has at least hundreds of r34 of them. IIRC the most popular ones from gen 1 outside from Charizard are Sandshrew/slash, Lapras and Nidoqueen. As for gen 2 Cyndaquil/Chikorita line are popular, followed by Furret/Mareep line, Suicine, Blissey and Celebi.

Monki said:

Also when and how did the Vaporeon meme come about? I get being horny for something with feminine curves and other features but why a fish-cat creature?

Vaporeon meme started after Gen 2 breeding mechanics (and subsequently, the Egg Groups) are introduced. The explanation are in the meme itself, but basically it's something of Pokedex says combined with game mechanics meets horny. Doesn't stop people from using that meme practically everywhere else, though.