In the Trophy Garden. Bring Quick Balls they work well.
Pichu evolves by happiness.
That Pokemon is pichu.
you get it at trophy garden
in mrs bachlot mansion
not hard
in pokemon pearl/diamond it is in the trophy garden
when it has high friendship
you can get it at the trophy garden
Breed it with a Voltorb
arceus or shiny pichu event
breed two pikachus holding magnets and the pichu will have it
http://www.youtube.com/watch?v=7yaRbkh4pi4