just run around in the tall grass he'll appear after a while(if you give him a thunderstone he evolves into a raichu but can't learn any new moves except for tms and HMS
in the safari zone
Head southwest, or south east
At the first pile of grass you see
i believe it is sapphire, that shadow pickachu is in. he is somehwere in the safari zone.
I think you can get one at the Safari Zone. Go to the first patch of grass you see. I have caught them there before.
after beating the fortree gym, go to the safari zone (you need a pokeblock case) and catch it in the grass.
IT is in the safari area near lilcove city
you can find pickachus in the safari zone who have a 5% chance of carrying one. (but you might like to know this too, there is a 5% chance of finding a pickachu in the safari zone, so 2.5/1000 Pokemon you face in the safari zone have a light ball, try trading from a friend instead if you can, else.....it'll take a long time...since you cant use a pokemons frisk ability)
They attract rare Pokemon (ex pickachu and the like)... I'm not sure whether the pokeblock level has any affect... It could, I'm not sure
roam in the safari zone. there is no exact place where you find a phanpy in safari zone
ruby, common in safari zone sapphire, common in safari zone emerald, common in safari zone
You can find a Jigglypuff in the Johto Safari Zone in Pokémon HeartGold and SoulSilver in the Meadow and Swamp areas of the Safari Zone.