23: Ekans 25: Pikachu

Arbok

24: Arbok

Kanto

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

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