The egg groups are a classification used in the Pokémon games that defines which Pokémon are compatible with others when it comes to breeding. If two Pokémon are not in an identical egg group, they cannot breed at all. One Pokémon can be of one or two groups.
The fact that two Pokémon are part of the same egg group originates the egg moves, that are those moves a Pokémon can inherit from the father, even though the mother doesn't know them. In the sixth generation games, the moves can be inherited from either the father or the mother.
Here are some examples:
|Venusaur ♂||+||Breloom ♀||=||Shroomish|
|Seed Bomb||Seed Bomb|
|Aggron ♂||+||Haxorus ♀||=||Axew|
|Iron Tail||Iron Tail|
|Xatu ♂||+||Noivern ♀||=||Noibat|
|Scrafty ♂||+||Floatzel ♀||=||Buizel|
List of egg groups
The Undiscovered (No Eggs in Pokémon Stadium 2) Egg Group consists of 110 Pokémon.
The Pokémon in this egg group can't breed. That means they will never have an Egg, not even with a Ditto. The list of them consists of Legendary Pokémon (with the exception of Manaphy and Phione), Mythical Pokémon, Baby Pokémon, Ultra Beasts and various other Pokémon such as exclusive forms of Pokémon like the Cosplay and Cap variants of Pikachu.
The Ditto egg group consists of only one Pokémon: Ditto.
The bug egg group consists of 77 Pokémon, most of them being Bug-type Pokémon, if not, at least that have physical bug-like appearance.
The flying egg group consists of 57 Pokémon. Consists mainly of species based on birds, but may also contain other winged creatures (like bats and pterosaurs). The only Pokémon of this egg group that is not a Flying type is Decidueye, however, its pre-evolutions are.
The human-like (humanshape in Pokémon Stadium 2) egg group consists of 52 Pokémon. As the egg group's name suggests, species in this egg group are fully bipedal, with two arms and two legs. Most of this group's Pokémon are Psychic or Fighting types.
The mineral egg group consists of 56 Pokémon. Species in this group are based on inorganic objects with a solid structure. A large proportion of species in this group are genderless, meaning that Egg moves are not passed down as easily. Most of this group's Pokémon are Rock-, Ice-, Steel- and Ground-type Pokémon.
The amorphous (indeterminate in Pokémon Stadium 2) egg group consists of 52 Pokémon. Species are typically based on enigmatic objects like blobs, gases and ghosts. Most of these Pokémon are Poison-, Psychic- and Ghost-type Pokémon.
The field (ground in Pokémon Stadium 2) egg group consists of 218 Pokémon. Most of those Pokémon are terrestrial and are based on mammals, although some reptile and bird-based species also belong to this group.
The water 1 egg group consists of 95 Pokémon. It is formed mostly by Water-type Pokémon capable of moving on land and in the water. Species are therefore mostly based on amphibians, with some aquatic mammals, reptiles and birds.
The water 2 egg group consists of 27 Pokémon. It is formed mostly by Water-type Pokémon that can only move around in water, thus many species based on fish belong to this group.
Egg group 10. The water 3 egg group consists of 34 Pokémon. It is formed partly by Water-type Pokémon. This egg group also includes over half of the fossils. Species are based on current or historic aquatic invertebrates.
The monster egg group consists of 79 Pokémon. The Pokémon in this egg group typically feature one or more reptilian traits, such as a large tail for balance, claws on limbs, bristled backs or strong jaws.