How do you catch Mewtwo in heartgold?

You can't actually catch Mewtwo in Pokémon HeartGold. Mewtwo is a legendary Pokémon that is not available in that game.

To catch Mewtwo, you'll need to play Pokémon: Let's Go, Pikachu! or Let's Go, Eevee!, or the original Pokémon Red, Blue, or Yellow versions.

Here's why:

* Mewtwo's origin: Mewtwo was created by scientists in the original games, and it is primarily associated with those games.

* HeartGold's story: HeartGold follows the story of the original Gold and Silver games, which don't feature Mewtwo.

If you want to experience the thrill of catching Mewtwo, you'll need to play one of the games mentioned above. Remember, catching Mewtwo is a challenging task and requires careful preparation and strategy.