Originally Posted by LAX
I don't think neither of them is true, you need to defeat all the trainers on the bridge then help the man in the grass on the left side of the bridge...
You are wrong.
All you need to do is buy 1 potion, make sure Pikachu is already at full health. Keep giving him this 1 potion over and over. Repeat this about 20 times. Your pikachu will just adore you, and you get the Bulbasaur.