POKEMON RED AND BLUE
Chansey can be caught in the Safari Zone and the Unknown Dungeon.

POKEMON YELLOW
Chansey can be caught in the Safari Zone and the Unknown Dungeon.  She appears in all the Poke Centers in the game.

POKEMON GOLD AND SILVER
Chansey can be caught in Routes 13, 14, and 15.  She also appears in both Game Corners.  When you have 2 sevens in a row on the Slot Machine, Chansey may appear and throw some eggs up in the air to try to help you get 3 sevens in a row.

POKEMON SNAP
Chansey can be found in the Beach level.  Near the end of the level, you'll see Eevee chasing a pink ball.  Hit the ball with a Pester Ball and Chansey will appear from the it.

POKEMON TRADING CARD GAME GB
You can get the Chansey card in a booster pack.

POKEMON PINBALL
Chansey appears in the Safari Zone level.

POKEMON STADIUM
You can use Chansey to fight in battles.

POKEMON STADIUM 2
You can also use Chansey to fight in battles.  Chansey appears in the mini-game "Egg Emergency."

POKEMON PUZZLE CHALLENGE
Chansey is shown with Nurse Joy in the Pokemon Center.