Ilex Forest: 24 species in 3 games

Gold and Silver Crystal HeartGold and SoulSilver

24 species, 5 versions

Gold and SilverCrystalHeartGold and SoulSilver

Gold and Silver: 12 species
Species	Method	Levels	Chance	Game page
Caterpie	Headbutting a high encounter rate tree	10	50%	All places
Caterpie	Headbutting a low encounter rate tree	10	65%	All places
Caterpie	Headbutting a normal encounter rate tree	10	65%	All places
Caterpie	Walking in tall grass or a cave	5 to 6	up to 60%	All places
Metapod	Headbutting a low encounter rate tree	10	15%	All places
Metapod	Headbutting a normal encounter rate tree	10	15%	All places
Metapod	Walking in tall grass or a cave	5 to 6	up to 30%	All places
Butterfree	Headbutting a high encounter rate tree	10	5%	All places
Butterfree	Headbutting a low encounter rate tree	10	5%	All places
Butterfree	Headbutting a normal encounter rate tree	10	5%	All places
Zubat	Walking in tall grass or a cave	5 to 6	up to 25%	All places
Oddish	Walking in tall grass or a cave	5 to 6	60%	All places
Paras	Walking in tall grass or a cave	5 to 6	up to 15%	All places
Psyduck	Surfing	10 to 19	90%	All places
Golduck	Surfing	15 to 19	10%	All places
Poliwag	Fishing with a good rod	20	65%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Exeggcute	Headbutting a high encounter rate tree	10	15%	All places
Exeggcute	Headbutting a low encounter rate tree	10	15%	All places
Exeggcute	Headbutting a normal encounter rate tree	10	15%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Pineco	Headbutting a high encounter rate tree	10	30%	All places

Crystal: 18 species
Species	Method	Levels	Chance	Game page
Caterpie	Headbutting a high encounter rate tree	10	15%	All places
Caterpie	Walking in tall grass or a cave	5	up to 30%	All places
Metapod	Headbutting a high encounter rate tree	10	5%	All places
Metapod	Walking in tall grass or a cave	7	up to 20%	All places
Butterfree	Headbutting a low encounter rate tree	10	5%	All places
Butterfree	Headbutting a normal encounter rate tree	10	5%	All places
Weedle	Headbutting a high encounter rate tree	10	15%	All places
Weedle	Walking in tall grass or a cave	5	up to 30%	All places
Kakuna	Headbutting a high encounter rate tree	10	5%	All places
Kakuna	Walking in tall grass or a cave	7	up to 10%	All places
Beedrill	Headbutting a low encounter rate tree	10	5%	All places
Beedrill	Headbutting a normal encounter rate tree	10	5%	All places
Pidgey	Walking in tall grass or a cave	7	up to 5%	All places
Oddish	Walking in tall grass or a cave	5 to 7	50%	All places
Paras	Walking in tall grass or a cave	6	up to 5%	All places
Venonat	Walking in tall grass or a cave	5	30%	All places
Psyduck	Surfing	10 to 19	90%	All places
Psyduck	Walking in tall grass or a cave	7	10%	All places
Golduck	Surfing	15 to 19	10%	All places
Poliwag	Fishing with a good rod	20	65%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Hoothoot	Headbutting a high encounter rate tree	10	60%	All places
Hoothoot	Headbutting a low encounter rate tree	10	50%	All places
Hoothoot	Headbutting a normal encounter rate tree	10	50%	All places
Hoothoot	Walking in tall grass or a cave	7	5%	All places
Noctowl	Headbutting a low encounter rate tree	10	10%	All places
Noctowl	Headbutting a normal encounter rate tree	10	10%	All places
Pineco	Headbutting a low encounter rate tree	10	30%	All places
Pineco	Headbutting a normal encounter rate tree	10	30%	All places
Celebi	Static encounter	30	100%	All places

HeartGold and SoulSilver: 17 species
Species	Method	Levels	Chance	Game page
Caterpie	Headbutting trees	3 to 5	30%	All places
Caterpie	Walking in tall grass or a cave	5 to 6	up to 40%	All places
Metapod	Headbutting trees	3 to 5	10%	All places
Metapod	Walking in tall grass or a cave	5 to 6	up to 20%	All places
Butterfree	Headbutting trees	6 to 8	10%	All places
Zubat	Walking in tall grass or a cave	5 to 6	up to 20%	All places
Oddish	Walking in tall grass or a cave	5 to 6	up to 40%	All places
Paras	Walking in tall grass or a cave	5 to 6	up to 10%	All places
Psyduck	Surfing	5 to 20	90%	All places
Golduck	Surfing	10 to 20	10%	All places
Poliwag	Fishing with a good rod	20	60%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Magikarp	Fishing with a good rod	20	40%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Hoothoot	Headbutting trees	3 to 8	up to 60%	All places
Noctowl	Headbutting trees	6 to 8	10%	All places
Pineco	Headbutting trees	6 to 8	30%	All places
Numel	Walking in tall grass or a cave	6	20%	All places
Spoink	Walking in tall grass or a cave	5 to 6	20%	All places
Budew	Walking in tall grass or a cave	5 to 6	20%	All places
Carnivine	Walking in tall grass or a cave	6	20%	All places