1. Obtain the GS Ball.
- After defeating Pryce in the Mahogany Town Gym, return to New Bark Town.
- Professor Elm will give you the GS Ball.
2. Travel to the Johto Safari Zone.
- Head to Cherrygrove City and enter the gate on the right side of town.
- Use the GS Ball on the pedestal in the middle of the Safari Zone.
3. Defeat the Legendary Beasts.
- Entei: Go to the Burned Tower and defeat Entei.
- Raikou: Head to the Power Plant and defeat Raikou.
- Suicune: Surf along the coast of Kanto until you find the Tin Tower. Defeat Suicune inside.
4. Return to New Bark Town.
- Talk to Professor Oak in his lab. He will reward you with a Shiny Celebi.
Note: The Movie Event in Pokemon Ash Gray is accessible after you have obtained all eight Kanto Gym Badges.