How do you get eeve in Pokemon Diamond?

Answer 1

first of all its eevee and you can either get one from bebe, her house is the one next to the pokecenter in hearthome city after you obtain the natinal dex or when you go to the pokemon mansion and you talk to the owner and say yes to both his questions then he will tell you that there is a rare pokemon in the trophey garden (the pokemon is different everyday so if it is not eevee the first time try again tomorrow) then the dude beside him will leave, go out side of the room then back in and talk to the dude beside to owner and he will say that there were some ------ in the trophey garden then go to the trophey garden and you will be able to find that pokemon.

P.S. the pokemon mansion thing only works if you have the natinal dex

Hope this helped :D