Train mareep
Transfer it from emerald OR trade it from soul silver or heart gold
You can't find registeel in Pokemon HeartGold.
You can find it in Pokemon Platinum, Pokemon Crystal, Pokemon HeartGold, and Pokemon SoulSilver.
unkowns {pokemon}
You cannot find Latios in Pokemon HeartGold unless you went on wi-fi and got the Enigma Stone
There is no such thing.
You can't
yes
trade
You can't
Just find them!
You can't do it.