You only get it by breeding Chansey.
breed Chancey or blissey with luck incense
You need to breed Chansey.
You cant catch a happiny you have to breed a Chansey while the Chansey is holding a luck incense.
You find it in the Pokemon mansion. I'm not to sure but that is the place to find Happiny in diamond and pearl.
No
happiny and riolu
Happiny is in Trophy Garden as one of the Daily Pokemon.
An oval stone enables certain Pokemon to evolve. The only one I know of is Happiny.
Mt Coronet.
Happiny did not exist at the time of Pokémon Crystal. Therefore, it cannot be obtained.
The hiker (in Pokemon Diamond, Pearl and Platinum) to find a Happiny will be on Route 210, South Pokemon with Breeder Kahlil.
You can find a Happiny in White forest. Not Black City, just White Forest. Enjoy!! xD