I don't know if it is the same on heart gold as it is on soul silver, but the Pokemon that hatched for me was a togepi.
Hope I helped!
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!!
you put a ditto with typhlosion
Deposit one of your Pokemon and you may get the egg
You need an egg for both Pichu and Cleffa. :)
you dont you get a cleffa from diamond/pearl,and or platinum
Normal egg groups, same as Diamond, Pearl, Platinum, HeartGold, and SoulSilver.