Mr. Pokemon's Discovery
Inside Mr. Pokemon's house, you are greeted and given the MYSTERY EGG by Mr. Pokemon. Then, as you are just about ready to leave, Professor Oak comes over to say hello. He sees the Pokemon you have for a partner, and thinks you will be a good Pokemon trainer. Professor Oak gives you the POKEDEX, and leaves for Goldenrod City.
When you step outside to begin home to give Professor Elm the MYSTERY EGG, he calls you on the phone, informing you of a Pokemon robbery at the lab. That red-haired character whose foot you're still sore from? Make your way back to Cherrygrove City, and continue east to New Bark Town. As soon as you step beyond the border of Cherrygrove, that suspicious character shows up and challenges you.
If you chose Chikorita, he'll have Cyndaquil. Cyndaquil, Totodile. Totodile, Chikorita. Chikorita, you get the picture. After defeating ??? head to the lab. There a police man will be talking to Professor Elm. Give the man ???'s name (don't name him ???), and he'll leave.
Talk to Professor Elm to give him the MYSTERY EGG to study. He'll comment on how Professor Oak gave you the POKEDEX, and the aide will give you 5 POKEBALLs before you leave to begin your new quest.
Head back to Cherrygrove City. Battle and capture wild Pokemon. Make sure you give all of your Pokemon equal experience! (I have friends who make the mistake of raising a level 55 Typhlosion, and leaving the rest of his roster in the low 20s). Travel north to where the two trainers had been battling. They should be done now, and each of the two should challenge you.
The first one has a L4 Rattata, and #2 has a L2 Rattata and L2 Pidgey. Two more bug catchers wait ahead. The first with two L2 Caterpie, and the second with three L2 Caterpie and a L3 Weedle. Continue north and west to Violet City, where there is much yet to be done.