There is no GameShark for Misty to follow you OR Brock.
Pokemon Yellow was SUPPOSED to make you like Ash, but it's just a harder version of Pokemon Red/Blue (The gym leaders were bad quite a bit harder in Yellow, Saffron city had quite a gym :P)
It's just that the main character in Pokemon is just a normal person LIKE Ash, but he really isn't.
Devon Of GameShark: Doctor FAIL
This is not a drill: People are using GameShark codes incorrectly, THIS IS NOT A DRILL!! WE'RE DOOMED!
Not to worry, Doctor Devon is here to save the day! He's here to help the patients