Breeding

Introduction

Breeding produces eggs at Day Care. You control IV inheritance, natures, abilities, and egg moves. It's how you optimize competitive teams, hunt shinies (Masuda method), and get moves outside normal learnsets.

Polished Crystal changes:

Mirror Herb – Transfer egg moves between parents at Day Care
Ability Capsule/Patch – 25% chance per parent to pass Hidden Ability
Mr. PKMN's 6IV Shiny Ditto – Trade Red Scale for perfect breeding stock
Nidorina/Nidoqueen breedable – Now in Monster/Field groups (vanilla had them in Undiscovered)
Form inheritance – 50/50 when same-species parents have different forms
Pokéball inheritance – Offspring can inherit ball from either parent

Egg Groups

Egg groups determine breeding compatibility. Two Pokémon breed if they share at least one group (except Undiscovered). Offspring species comes from the female parent (or non-Ditto parent when breeding with Ditto).

15 egg groups:

Monster – Bulbasaur, Charmander, Nidoran-M
Water 1 – Squirtle, Totodile, Marill
Bug – Caterpie, Weedle, Scyther
Flying – Pidgey, Spearow, Hoothoot
Field – Pikachu, Eevee, Growlithe
Fairy – Clefairy, Togepi, Snubbull
Grass – Oddish, Chikorita, Sunflora
Human-Like – Machop, Hitmonlee, Mr. Mime
Water 3 – Tentacool, Shellder, Corsola
Mineral – Geodude, Onix, Shuckle
Amorphous – Gastly, Grimer, Wobbuffet
Water 2 – Goldeen, Magikarp, Qwilfish
Ditto – Ditto only, breeds with most groups
Dragon – Dratini, Larvitar, Kingdra
Undiscovered – Cannot breed (babies and legendaries): Pichu, Togepi, Lugia

Pokémon in multiple groups act as breeding bridges. Marill (Water 1 + Fairy) can transfer egg moves between those groups.

Compatibility Checker

Use the interactive tool below to find all Pokémon that can breed with your selected species. Results are grouped by shared egg group, making it easy to identify potential breeding partners for egg moves or building breeding chains.

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Gender Ratios

Gender ratios affect breeding efficiency since offspring species comes from the female parent (or non-Ditto parent).

100% Female / 0% Male – Chansey, Miltank (must use Ditto)
87.5% Female / 12.5% Male – Starters: Chikorita, Cyndaquil, Totodile
75% Female / 25% Male – Clefairy, Vulpix
50% Female / 50% Male – Pikachu, Eevee, most Pokémon
25% Female / 75% Male – Growlithe, Abra
12.5% Female / 87.5% Male – Kanto starters: Bulbasaur, Charmander, Squirtle
0% Female / 100% Male – Tauros, Tyrogue (must use Ditto)
Genderless – Magnemite, Staryu, Porygon (must use Ditto)

Egg Move Inheritance

Egg moves are moves only accessible through breeding. Male parent moves transfer first, then female moves. The move must be in the offspring's egg move pool.

Rules:

Male parent moves take priority
Move must exist in offspring's egg move pool
Offspring hatch with inherited moves already learned
Multiple egg moves transfer when both parents have moves in the pool

Mirror Herb

Mirror Herb transfers egg moves between parents at Day Care:

Give it to one parent at Day Care
Each step has 1/256 chance to transfer an egg move from one parent to the other
Teaches egg moves to parents without breeding new offspring
Faster than chain breeding for multiple egg moves

Chain breeding is sometimes still needed. If Pokémon A knows a move but can't breed with Pokémon B, breed A with C (which shares groups with both), then breed C with B. Mirror Herb usually eliminates this.

Hatch Cycles and Steps

Eggs hatch after a certain number of cycles. Each cycle is ~256 steps.

10 cycles (2,560 steps) – Magikarp, Pichu
20 cycles (5,120 steps) – Most common Pokémon
40 cycles (10,240 steps) – Starters, Eevee, Dratini, Lapras, Aerodactyl
80 cycles (20,480 steps) – Larvitar, Chansey, Snorlax

Faster hatching:

Flame Body or Magma Armor in party: 50% reduction
Oval Charm: 2× multiplier
Both stack: 4× faster hatching

Ditto Breeding

Ditto breeds with any Pokémon outside Undiscovered group:

Male-only: Tauros
Female-only: Chansey
Genderless: Magnemite, Staryu, Porygon
Skewed gender ratios (easier than finding females)

Non-Ditto parent determines offspring species. Ditto can't pass egg moves—use two compatible Pokémon for that.

Find Ditto on Route 35 (Pokégear radio's Pokémon Music channel) or Cerulean Cave postgame.

Mr. PKMN's Perfect Shiny Ditto

Mr. PKMN trades Red Scale for 6IV Shiny Ditto:

31 IVs in all stats (perfect for breeding)
Shiny + different OTID activates Masuda method (higher shiny odds)
Get Red Scale from Red Gyarados at Lake of Rage

Baby Pokémon and Incense Items

Most baby Pokémon hatch normally without items. Only Pichu needs Light Ball on Pikachu/Raichu.

Baby Pokémon that hatch without items:

Cleffa (from Clefairy/ Clefable)
Igglybuff (from Jigglypuff/ Wigglytuff)
Togepi (from Togetic/ Togekiss)
Tyrogue (from Hitmonlee/ Hitmonchan/ Hitmontop)
Smoochum (from Jynx)
Elekid (from Electabuzz)
Magby (from Magmar)

Without incense where needed, you get the evolved form.

Day Care Locations

Day Care is in Goldenrod City's south side. Route 34 below it is good for hatching.

Compatibility messages:

"They seem to get along very well!" – Same species, different OTs (fastest eggs)
"They seem to get along." – Same species same OT, or different species different OT
"They don't seem to like each other." – Different species, same OT (slow eggs)
"They prefer to play with other Pokémon." – Incompatible (no eggs)

Competitive Breeding

Battle-ready Pokémon need specific IVs, natures, and abilities.

IV Inheritance

IVs (Individual Values) range 0–31 per stat. Higher = better stats at level 100.

How IVs pass down:

Default: Three random IVs from parents
Destiny Knot: Five IVs from parents (one still random)
Power items (Power Weight, Power Bracer, etc.): Guarantees specific stat IV from holder

Method:

Get parents with good IVs (or use Mr. PKMN's 6IV Ditto)
Give one Destiny Knot
Breed until offspring has better IVs
Replace parent with better offspring
Repeat

Nature Inheritance

Natures give +10% to one stat, -10% to another.

Common competitive natures:

Adamant (+Attack, -Sp. Atk): Physical attackers
Jolly (+Speed, -Sp. Atk): Fast physical attackers
Modest (+Sp. Atk, -Attack): Special attackers
Timid (+Speed, -Attack): Fast special attackers
Bold (+Defense, -Attack): Physical walls
Calm (+Sp. Def, -Attack): Special walls

Passing nature: Everstone on parent = 100% nature inheritance.

Catch wild Pokémon with Synchronize (Abra from Goldenrod Game Corner) to get specific natures easier.

Ability Inheritance

Ability Capsule/ Ability Patch on parent: - 25% chance for Hidden Ability offspring - 50% if both parents hold one

Female (or non-Ditto) parent:

60% chance to pass its current ability

Get Hidden Abilities from Wonder Trade (33% chance) or wild encounters (5% chance).

Form Inheritance

Same-species parents with different forms: 50/50 chance for each form.

Different species: Female (or non-Ditto) parent's form.

Everstone only affects nature, not form.

Pokéball Inheritance

Same species: Either parent's ball (50/50).

Different species: Female (or non-Ditto) parent's ball.

Shiny Breeding - Masuda Method

Masuda method increases shiny odds through different OTIDs (Original Trainer IDs).

In Polished Crystal:

Needs different OTIDs, not different languages
Mr. PKMN's Shiny Ditto has different OTID = auto-activates method
Much higher shiny chance than normal breeding/wild encounters
Stacks with Shiny Charm
Parent shininess doesn't affect offspring IVs

Optimized Breeding Workflow

Get Mr. PKMN's 6IV Shiny Ditto (trade Red Scale from Red Gyarados)
Catch Synchronize Pokémon for each nature you need (Abra at Goldenrod Game Corner)
Give target nature parent Everstone
Get egg moves via breeding or Mirror Herb
Use Ability Capsule/Ability Patch for Hidden Ability (25% chance per parent)
Give other parent Destiny Knot, breed with 6IV Ditto
Hatch with Flame Body/Magma Armor + Oval Charm (4× faster)

Nidoran Breeding Mechanics

Nidoran-F eggs hatch as either sex (50/50).

Nidorina and Nidoqueen can breed (Monster/Field groups). This differs from main games where they can't breed.

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