Pallet Town & Route 1

From Pokémon HeartGold & SoulSilver Wiki

Pallet Town

Prof. Oak's Lab

After you get the 16th gym badge you will receive a call from Prof. Oak asking you to meet him in his lab. Head to Pallet Town and visit him in the Lab. After a brief talk receive HM08 Rock Climb. Oak will inform you about a mystery trainer that is beating everyone, at the top of Mount Silver.

Getting Kanto Starter

After you have obtained 16 badges and defeated Red, head to Prof. Oak's Lab. He'll give you a choice of either Bulbasaur, Charmander, or Squirtle. Whichever one you choose it will be at Lv. 5.

You must defeat Red before you can get a starter from Oak. Otherwise Oak will just keep saying what he says after he gives you the Rock Climb HM.