When you get here go through the grass to get to a house, pick the berry off the berry tree then go inside, there is a man who will give you another berry, if you want to go to Mr Pokémon's house go to the East path, the other is blacked by 2 trainers battling, when you get to the house pick the PSNcureberry from the tree then go inside.
Mr Pokémon will give you a mystery egg, you will have to give it to Professor Elm, then a professor called Professor Oak will talk to you and give you the Pokédex.
When you go outside Professor Elm will say that there's been a disaster so go back to the Lab.
Hoppip
Pidgey
Poliwag*
Caterpie
Hoothoot
Weedle
Spinarak***
Ledyba**
