Blue: Caterpie (15%), Pidgey (40%), Rattata (45%)
FireRed & LeafGreen: Pidgey (45%), Rattata (45%), Caterpie (5%), Weedle (5%)
Nuzlocke Warning: The patch of grass on the other side of Viridian Forest is part of Route 2 and contains the same Pokémon. If you catch a Pokemon in the bottom half of the route, you can't catch one in the top half.
Route 2 Diglett Cave Entrance Edit
After going into Diglett Cave's Vermilion City entrance and coming out on the other side, you will find yourself on Route 2 again. Going southward will lead you to a small house and a gate. Inside the house is a man who want's to trade his Mr. Mime for your Abra. Remember, though, depending on your rules, if you caught a Pokémon on Route 2 the first time you were there, you might not be able to trade for a Mr. Mime . In Yellow, however, he asks for a Clefairy instead of an Abra. Further down the pathway is a gate with one of Professor Oak's aides inside. If you have caught ten or more Pokémon (alive or dead), he will give you HM05 Flash. Flash is technically not a "necessary" HM, as the only place its needed is Rock Tunnel, and you can get through without it, but Flash facilitates the process tenfold. There are also items that you can access after passing through the gate and continuing southward, so make sure you pick those up!