In the RPGs, starting with the second generation of games, Pokémon can also be obtained through breeding. There are several benefits to breeding:
- It allows you to gain "baby" forms of Pokémon, such as Pichu.
- It allows a Pokémon to learn moves that it cannot normally learn.
Each Pokémon is organized into one or two egg groups, and, with few exceptions, if two Pokémon are in the same egg group, they may breed. However, note the following:
- With the exception of Ditto, breeding requires a male Pokémon and a female Pokémon.
- Ditto may breed with any Pokémon not in the "unbreedable" group. That is, genderless Pokémon may only breed with Ditto. Two Ditto may not breed together.
- The "unbreedable" group is exactly what it means: the Pokémon may not be bred.
In the second generation of games, two Pokémon with identical Defense Individual Values and identical or off-by-eight Special IVs may not breed. This is to prevent a parent from breeding with its child.
When two Pokémon breed, the resulting egg will have the species of its mother, if Ditto is not involved, or the non-Ditto parent, if Ditto is involved. With the exception of Azurill and Wynaut, the egg will also be of its least evolved form. However:
- The offspring of a Nidoran♀ may be a Nidoran♀ or Nidoran♂.
- Likewise, the offspring of an Illumise may be an Illumise or a Volbeat.
- The offspring of a Marill or Azumarill will be a Marill, unless either parent is holding the Sea Incense item, in which case the offspring will be a Azurill.
- Likewise, the offspring of a Wobbuffet will be a Wobbuffet, unless either parent is holding the Lax Incense item, in which case the offspring will be a Wynaut.
The baby Pokémon, after hatching from an egg, will be at Level 5, and will start with a happiness value of 120.
Getting an EggEdit
In the second generation, after both parents have been deposited in the Daycare, a random number between 1 and 255 is generated, representing the number of steps that your character must walk before a second random number between 0 and 255 is generated. This second random number is then compared to a preset number called the breeding value, and if the random number is lower, then an egg is created.
In the third generation, after both parents have been deposited in the Daycare, a random number between 0 and 100 is generated every 256 steps your character takes. If this number is less than the breeding value, an egg is created. Note that this random number is not uniformly distributed: in reality, a uniformly distributed random number between 0 and 65535 is created, and then multiplied by 100/65535 using integer multiplication and division.
To determine the breeding value, check if the two parents are of the same species and have identical IDs, and look in the following table. For this purpose, Nidoran♀ and Nidoran♂ are considered to be the same species, as is Volbeat and Illumise.
For an egg to hatch, your character must move some number of hatch steps, depending on the type of Pokémon. In Emerald, if your Pokémon has either the Magma Armor or the Flame Body abilities, the number of steps indicated on the Pokémon's entry page is halved. Note that all Pokémon will have hatch steps data, but is generally useless for those that cannot breed.
Certain Individual Values for Pokémon may be inherited from either parent, with the remainder of the IVs being determined at random.
- In the second generation of games, the Defense IV of the offspring is inherited the parent of the opposite gender (if breeding with a Ditto, then the IV is inherited from Ditto). The Special IV of the offspring is also similarly inherited, but there is a 50% chance that the IV will be altered up or down by 8.
- In Pokémon Ruby, Sapphire, FireRed, and LeafGreen, two or three randomly chosen IVs may be inherited from the parents, with each parent contributing at least one. In Emerald, the offspring always inherits three IVs. (The same IVs may be inherited from both parents in RS/FL, thus only in such a case will a Pokémon only inherit two IVs).
The personality trait of a Pokémon may also be inherited in Emerald. If a Ditto or a female Pokémon is holding the Everstone item, then the offspring will have the personality of that parent. If the parents are Ditto and a female Pokémon, and both are holding the Everstone item, then the offspring will have a 50% chance of inheriting the personality from either parent.
The main reason for breeding, however, remains with the inheritance of moves. Normally, a baby Pokémon will have the default starting moves as stated on the Pokémon's entry page. However, moves may be inherited as follows:
- If the baby Pokémon can learn an attack from levelling up, and both of its parents currently have that attack in their movesets, then the baby will inherit that attack.
- If the baby Pokémon can learn a Technical or Hidden Machine move, and the male parent currently has that attack in their moveset, then the baby will inherit that attack. (For the purposes of this criteria, the three attacks that can be learned from the move tutor in Crystal are considered to be Technical Machines).
- If the male parent currently has an attack that is found in the baby Pokémon's breeding list, which can be found in the Pokémon's entry page, then the baby will inherit that attack.
Note that no moves are passed down if one parent is Ditto and the other parent is female or genderless. In Emerald, if either parent holds the Light Ball item, then a baby Pichu will start with the Volt Tackle attack, even if neither parent has that move in its moveset.