Viridian Forest
Ok, so your in the big house with 2 people in it. They don't really give you anything good except stupid info. Walk out the door to your north. When you get out, there should be a guy by a tree. Talk to him and go left. Keep going until you reach a patch of tall grass. There should be Weedle's and Catarpie's in the grass. After you've caught them, go back to that tree that the guy was standing next to. After that, go up to the thin line of grass and walk around until you get attacked by a Pikachu(red and blue only). After you caught the Pikachu, go right.