Route 12: 22 species in 1 game

Road 12: 22 species across 2 versions

X: 20 species
Species	Method	Levels	Chance	Game page
Tentacool	Surfing	25 to 27	84%	All places
Slowpoke	Walking in tall grass or a cave	23 to 25	30%	All places
Slowpoke	Walking in yellow flowers	27	10%	All places
Exeggcute	Walking in tall grass or a cave	24	10%	All places
Exeggcute	Walking in yellow flowers	26	10%	All places
Pinsir	Walking in tall grass or a cave	25	5%	All places
Pinsir	Walking in yellow flowers	27	5%	All places
Tauros	Encountering 5 pokemon within grass, flowers, or within a cave	14	5%	All places
Tauros	Walking in tall grass or a cave	25	10%	All places
Tauros	Walking in yellow flowers	25 to 27	30%	All places
Lapras	Receive as a gift	30	100%	All places
Lapras	Surfing	27	1%	All places
Mareep	Encountering 5 pokemon within grass, flowers, or within a cave	13	35%	All places
Corsola	Fishing with a super rod	35	60%	All places
Remoraid	Fishing with a good rod	25	65%	All places
Octillery	Fishing with a super rod	35	35%	All places
Miltank	Encountering 5 pokemon within grass, flowers, or within a cave	14	5%	All places
Miltank	Walking in tall grass or a cave	25	10%	All places
Miltank	Walking in yellow flowers	25 to 27	30%	All places
Wingull	Encountering 5 pokemon within grass, flowers, or within a cave	13	60%	All places
Clamperl	Fishing with a good rod	25	35%	All places
Huntail	Fishing with a super rod	35	5%	All places
Luvdisc	Fishing with an old rod	15	100%	All places
Pachirisu	Walking in tall grass or a cave	23 to 24	5%	All places
Pachirisu	Walking in yellow flowers	25 to 26	5%	All places
Chatot	Walking in tall grass or a cave	23 to 25	30%	All places
Chatot	Walking in yellow flowers	27	10%	All places
Mantyke	Surfing	27	15%	All places
Dwebble	Smashing rocks	23 to 25	66%	All places
Binacle	Smashing rocks	23 to 25	34%	All places

Y: 20 species
Species	Method	Levels	Chance	Game page
Tentacool	Surfing	25 to 27	84%	All places
Slowpoke	Walking in tall grass or a cave	23 to 25	30%	All places
Slowpoke	Walking in yellow flowers	27	10%	All places
Exeggcute	Walking in tall grass or a cave	24	10%	All places
Exeggcute	Walking in yellow flowers	26	10%	All places
Tauros	Encountering 5 pokemon within grass, flowers, or within a cave	14	5%	All places
Tauros	Walking in tall grass or a cave	25	10%	All places
Tauros	Walking in yellow flowers	25 to 27	30%	All places
Lapras	Receive as a gift	30	100%	All places
Lapras	Surfing	27	1%	All places
Mareep	Encountering 5 pokemon within grass, flowers, or within a cave	13	35%	All places
Heracross	Walking in tall grass or a cave	25	5%	All places
Heracross	Walking in yellow flowers	27	5%	All places
Corsola	Fishing with a super rod	35	60%	All places
Remoraid	Fishing with a good rod	25	65%	All places
Octillery	Fishing with a super rod	35	35%	All places
Miltank	Encountering 5 pokemon within grass, flowers, or within a cave	14	5%	All places
Miltank	Walking in tall grass or a cave	25	10%	All places
Miltank	Walking in yellow flowers	25 to 27	30%	All places
Wingull	Encountering 5 pokemon within grass, flowers, or within a cave	13	60%	All places
Clamperl	Fishing with a good rod	25	35%	All places
Gorebyss	Fishing with a super rod	35	5%	All places
Luvdisc	Fishing with an old rod	15	100%	All places
Pachirisu	Walking in tall grass or a cave	23 to 24	5%	All places
Pachirisu	Walking in yellow flowers	25 to 26	5%	All places
Chatot	Walking in tall grass or a cave	23 to 25	30%	All places
Chatot	Walking in yellow flowers	27	10%	All places
Mantyke	Surfing	27	15%	All places
Dwebble	Smashing rocks	23 to 25	66%	All places
Binacle	Smashing rocks	23 to 25	34%	All places