you dont you get a cleffa from diamond/pearl,and or platinum
You need an egg for both Pichu and Cleffa. :)
Breed a Clefairy with a Jigglypuff.
You don't find Cleffa in the wild, but if you get a Clefairy at Mt. Moon and breed it with a Ditto, you will get a Egg that will hatch into a Cleffa. (This is my opinion, but hatching a Egg in Pokémon Silver seems so easy!!) In Pokémon Silver, Cleffa looks so cute!
No legendary can lay an egg except for manaphy which gives an egg to phione and you can not get manaphy or phione in heartgold
A Togepi.
Transfer in a pokémon that is holding a Lucky Egg.
Wild Chansey
In HeartGold, give a Mantine the Wave Incense and breed it. The egg with hatch into a Mantyke.
You get an egg from Professor Elm's assistant from any Poke Mart.
You can't it is an egg! Eggs cannot hold anything moron!!
Cleffa is a Normal type pokemon.
No. It's always gonna be Cleffa. In other games maybe, but not in Diamond or Pearl or any region ahead of Sinnoh.