Like how FireRed and LeafGreen could link up with Ruby, Sapphire, and Emerald to complete the Pokédex by trading regionally exclusive Pokémon, HeartGold and SoulSilver can link up with Diamond, Pearl, and Platinum to obtain Pokémon unavailable in Johto and Kanto (such as the Sinnoh starters) and vice versa. HeartGold and SoulSilver, as well as Gold and Silver, have Gym Leader or Elite Four specialists for every type that existed at the time except the Ground type. In the house to the left of the Pokemon Center, you'll find a boy will trade you his Onix for your Bellsprout. Because Elm feels that it's too dangerous for you to go alone, he'll allow you pick one of his Pokemon - Chikorita, Cyndaquil or Totodile - to act as your companion.

Whether she is chosen to be the player character or not, this new character will still appear in the game. However, this time it can also be used to collect Pokémon from Hoenn and Sinnoh after the National Pokédex is acquired. Reason: Do HGSS feature the same issues trading with Korean games, as present in previous Generation IV games?The previous games, Diamond, Pearl, and Platinum, only allowed the player to transfer 6 Pokémon per Game Boy Advance game per 24 hours, while these games have lifted this restriction, allowed unlimited transfers per 24 hours.

While the POKéMON may think it is just playfully nipping, its bite has enough power to cause serious injury. The Fighting Dojo in Saffron City takes a role similar to Sinnoh's Battleground, where the rematches between the player and Gym Leaders take place. While the Rainbow Wing and Silver Wing allow permission to climb the Bell Tower and enter Lugia's cave in the Whirl Islands, respectively, the player cannot encounter their version's respective mascot until they obtain the Clear Bell in HeartGold and the Tidal Bell in SoulSilver.

Because of HM05's conversion from Defog to Whirlpool, these games are the first in which all available HMs teach damaging moves (both Defog and Flash, contained in HM05, prevented this in previous games). Passing certain parts in the game can also affect the rematches by improving the team of the Trainers that can be re-battled.