Dudebro u can get shiny eevee which is eevee spelled backwards u can get it from this lady man figure called BEBE in pkmn diamond pearl and platinum in hearthome city idk what requirements though but i think u need to beat the elite 4 idk for sure and in Heart gold and soulsilver you can get it from BILL after u meet him in ecruteak city and then go to his house in goldenrod city and he will give u eevee
and what u can do is soft reset
On DS, you need to consecutively press L, R, Start, and Select (you have to hold them all down at once).
What this does is it reboots your game to the starting screen without you having to literally turn your DS off and on over and over again.
How does this help? Well, before you obtain the eevee from Bebe or Bill (please excuse my ignorance of how to get this in other games, I only know how to obtain it in HG, SS, D, P, and PT), save your game, and then collect the Eevee. If the Eevee isn't shiny, soft reset and try again. You only have a 1/8,192 chance of getting a shiny pokemon, including the Eevee that you want. It really isn't worth it, unless you hope to get extremely lucky on the first 1,000 or so tries, which I still wouldn't recommend, unless you really want that shiny Eevee.
After you get that shiny Eevee, max out its happiness. You can probably google that somewhere or ask another question as to how to max out happiness quickly in the game desired, and at night, level up your shiny Eevee and it should/will be a shiny Umbreon.