Friendship

Happiness is a measurement of how much a Pokémon loves its Trainer and enjoys being in their care. As a full feature, it was introduced in Generation II.

Generation I

A prototype of the happiness system used by later games was introduced in Pokémon Yellow, the last main series game of Generation I. Like the later system, its value ranged between 0 and 255 inclusive, however, this value was only applied to the Pikachu the player started with.

Unlike later games, since Pikachu is outside of its Poké Ball, the player can turn and look at it at any time as it follows him around the overworld. Pikachu will then indicate its happiness in a small window that appears. At maximum happiness, Pikachu will jump up and down before the window appears.

Like later games, Pikachu's happiness will rise when it gains a level. If its Trainer uses an item on Pikachu, its happiness will also rise, even if it is an item that has no effect on Pikachu (such as a Potion at full HP). In this manner, Pikachu is much easier to make happy than Pokémon in future generations.

Pikachu's happiness drops if it is put into Bill's PC or faints. Trading it to another game will reset its happiness to 0.

Happiness is not recorded for any other Pokémon in Generation I, while the happiness of Pikachu does not affect much: the only real effect it has is whether or not Melanie will give Bulbasaur away in Cerulean City, which she will only do if its happiness is 147 or higher.

Event	Change
Gaining a level	+5*
	+3*
	+2*
Using an item	+5*
	+3*
	+2*
Challenging a Gym Leader	+3*
	+2*
	+1*
Depositing in the PC	-3*
Depositing in the PC	-5*
Fainting	-1

Generation II

In Generation II the happiness system became fully implemented, building on the system used in Yellow by tracking the happiness of any Pokémon owned by the Trainer. Like before, it is a single byte with a value between 0 and 255.

Happiness is set when a Pokémon is brought under a Trainer's control: that is, it is 70 when a Pokémon is captured from the wild, and reset to 70 when a Pokémon is traded from another game. When a Pokémon is hatched from an egg, its value is set to 120. If a Pokémon is captured in a Friend Ball, rather than any other kind, its happiness is set to 200 instead.

Another function was given to happiness in Generation II, the evolution of certain Pokémon, which has continued until the present, with new Pokémon which evolve through happiness being introduced in each generation. Happiness-based evolutions occur when a Pokémon's happiness is 220 or higher.

Unlike in Generation I, happiness will not increase if an item that cannot be used is used on a Pokémon: for example, using HP Ups on a Quilava which already has the maximum HP it can have will not result in raised happiness.

Event	Change
Walking 256 steps	+1
Grooming, Daisy	+3
Grooming, older haircut brother	+5*
	+3*
	+1*
Grooming, younger haircut brother	+10*
	+3*
	+1*
Using vitamins	+5
Gaining a level	+5
Fainting	-1
Using EnergyPowder	-5
Using Heal Powder	-5
Using Energy Root	-10
Using Revival Herb	-15
Trading to another game	Reset to 70

Generation III

Happiness in Generation III works much the same as before, however, additions were made to happiness-altering events. If a Pokémon is caught in a Luxury Ball, all happiness-raising events will rise by one point more, while happiness-lowering events are not affected. Likewise, a Pokémon holding a Soothe Bell will also rise by one additional point per happiness-raising event. These effects stack on each other, meaning a Pokémon in a Luxury Ball holding a Soothe Bell gets two additional points per event.

Pokémon now have a base happiness per species, however, most catchable Pokémon have the standard 70 points as their starting level. The happiness value is used for Pokémon eggs from this point on to determine how long it will take them to hatch; as eggs cannot be affected by any other happiness-altering event besides walking, this is how steps for an egg to hatch are determined.

Event	Change
Walking 256 steps	+1
Grooming, Daisy*	+3*
Grooming, Daisy*	+2*
Using vitamins	+5*
	+3*
	+2*
Gaining a level	+5*
	+3*
	+2*
Using EV Berries	+2
Fainting	-1
Using EnergyPowder	-5
Using Heal Powder	-5
Using Energy Root	-10
Using Revival Herb	-15
Trading to another game	Reset to 70

Generation IV

Happiness in Generation IV is much the same as it is in Generation III, though the conditions are altered slightly. The Luxury Ball now causes a Pokémon to have a separate rise in happiness than Pokémon in other Balls.

In Eterna City, a girl in the Pokémon Center will give away a Pokétch app that shows how much the Pokémon in the player's party like the player. Maximum happiness is represented by two big hearts.

Dr. Footstep, the sole resident of the Footstep House on Route 213, will also tell a Pokémon's happiness, albeit in a roundabout way which differs among Pokémon species. At maximum happiness, he will give the Pokémon in question a ribbon.

Event	Change	Luxury Ball
Walking 256 steps	+1	+2
Massage, Veilstone City	+3	+5
Massage, Ribbon Syndicate	+5	+6
Using vitamins	+2	+6
Gaining a level	+2	+6
Using EV Berries	+2	+6
Using healing items	+1	+2
Fainting	-1
Using EnergyPowder	-5
Using Heal Powder	-5
Using Energy Root	-10
Using Revival Herb	-15
Trading to another game/Pal Park	Reset to 70

Pokémon Ranger: Shadows of Almia

Happiness also has a slight effect in the second Ranger game. The Partner Pokémon can have the condition of Happy or Very Happy. When it is happy, black musical notes come out of it. Multicolored musical notes come out when it is very happy. This may happen whether or not it is with the player. This condition increases the speed the Partner Gauge fills up.

Evolutions

Several Pokémon evolve when their happiness level is at or above 220:

Previous evolutions		Happiness evolution			Future evolutions
Zubat Poison Flying	→ Level 22	Golbat Poison Flying	→ Happiness	Crobat Poison Flying	Crobat does not evolve
Happiny Normal	→ Level up holding Oval Stone	Chansey Normal	→ Happiness	Blissey Normal	Blissey does not evolve
Eevee is the lowest in its line		Eevee Normal	→ Happiness (day)	Espeon Psychic	Espeon does not evolve
Eevee is the lowest in its line		Eevee Normal	→ Happiness (night)	Umbreon Dark	Umbreon does not evolve
Pichu is the lowest in its line		Pichu Electric	→ Happiness	Pikachu Electric	→ Thunderstone	Pikachu Electric
Cleffa is the lowest in its line		Cleffa Normal	→ Happiness	Clefairy Normal	→ Moon Stone	Clefable Normal
Igglybuff is the lowest in its line		Igglybuff Normal	→ Happiness	Jigglypuff Normal	→ Moon Stone	Wigglytuff Normal
Togepi is the lowest in its line		Togepi Normal	→ Happiness	Togetic Normal Flying	→ Shiny Stone	Togekiss Normal Flying
Azurill is the lowest in its line		Azurill Normal	→ Happiness	Marill Water	→ Level 18	Azumarill Water
Budew is the lowest in its line		Budew Grass Poison	→ Happiness (day)	Roselia Grass Poison	→ Shiny Stone	Roserade Grass Poison
Buneary is the lowest in its line		Buneary Normal	→ Happiness	Lopunny Normal	Lopunny does not evolve
Chingling is the lowest in its line		Chingling Psychic	→ Happiness (night)	Chimecho Psychic	Chimecho does not evolve
Munchlax is the lowest in its line		Munchlax Normal	→ Happiness	Snorlax Normal	Snorlax does not evolve
Riolu is the lowest in its line		Riolu Fighting	→ Happiness (day)	Lucario Fighting Steel	Lucario does not evolve