Generation II

Pending.

Generation III

Happiness in Generation III is a value between 0 and 255. Wild pokemon have their own base happiness, which is typically 70 (about 27%) for non-legendary first stage pokemon, but not always. If a pokemon hatches from an egg, its initial happiness ignores the base happiness value and is set to 120 (about 47%). When a pokemon is still in its egg, its happiness value is ignored (as there are no aspects in the game that apply happiness to eggs) and the happiness value is used as a decrementing step value that triggers the egg hatch when it reaches zero.

Happiness evolutions occur when happiness reaches 220 (about 86%).