The tree to the left of the house is a berry tree; you can pick one, and the man inside the house will give you another. Bear to the east behind his house, through the grasses, to find Mr. Pokémon's house. His tree will give you a Poison Cure Berry.
Mr. Pokémon will give you a mysterious egg, which you will have to take back to Professor Elm at his lab in New Bark Town. Professor Oak (our old friend from Pokémon RBY) is here visiting; he will give you a Pokédex.
When you step outside, your Pokégear will ring; it's Professor Elm! A disaster has struck the lab, and he asks you to return at once.
Hoppip
Poliwag
Caterpie
Weedle
Hoothoot
Spinarak
Pidgey
Zubat
Kakuna
Metapod
Ledyba