23: Ekans 25: Pikachu

Arbok

24: Arbok

Kanto

	HeartGold	SoulSilver	FireRed	LeafGreen	Crystal	Gold	Silver	Yellow	Red	Blue
Walking in tall grass or a cave
Cerulean Cave 1F									10% L52
Cerulean Cave B1F									5% L57
Route 23			5% L44						5% L41
Route 26		5% L30			+5% L30 +5% L30		+5% L30 +5% L30 +5% L30
Route 27		20% L28 +10% L28			+30% L28 +30% L28		+30% L28 +30% L28 +30% L28
Route 28					+10% L42 +10% L42
Route 3		5% L10			+5% L10 +5% L10		+5% L10 +5% L10 +5% L10
Route 4		5% L10			+5% L10 +5% L10		+5% L10 +5% L10 +5% L10
Victory Road 1F			5% L44
Victory Road 2F			5% L46
Victory Road 3F			5% L44

Johto

	Crystal	Gold	Silver
Walking in tall grass or a cave
Mt. Silver outside	+20% L42 +20% L42
Route 42	+5% L15 +5% L15

Sinnoh

	Platinum	Diamond	Pearl
Walking in tall grass or a cave
Great Marsh Area 1	+8% L30	+8% L24–26	+8% L24–26
Great Marsh Area 2	+8% L30	+8% L24–26	+8% L24–26
Great Marsh Area 3	+8% L29	+8% L22–24	+8% L22–24
Great Marsh Area 4	+8% L29	+8% L22–24	+8% L22–24
Great Marsh Area 5	+8% L28	+8% L20–22	+8% L20–22
Great Marsh Area 6	+8% L28	+8% L20–22	+8% L20–22