User blog comment:MrJ17/Putting Together PTD2 Storyline Information!/@comment-5201028-20120708211526/@comment-4751272-20120711001018

Slowpokes and Poliwags are easy to get in PTD1 and trained up to a high level before sent to PTD2, so they shouldn't be a problem. Finding te Eevees, though...

Also not sure, it's a rumour, but people say evolutions of Gen 1/2 Pokémon will be avaiable in PTD2. Example, Tangela will be able to evolve into Tangrowth. Just rumours here, so keep some Eevees for the (possible) Leafeon/Glaceon. :)