Why wont your Pokemon evolve in Pokemon LeafGreen?

Answer 1

Some pokemon don't evolve at all while others will evolve under certain circumstances whether its by: An item, an evolution stone, trade, or happiness. Haunter for example evolves to Gengar only when a player trades to another player. Togepi evolves from friendship which basically comes from winning battles and when the player gives them items and takes care of them. Evolution stones such as the Fire Stone can be purchased at the Celadon City Department Store on the 4th Floor. And lastly items such as the Kings Rock are special items that allow certain pokemon to evolve when there being traded such as Poliwhirl. Also if a pokemon that can evolve holds an Everstone the stone will prevent evolution in general so that could be the cause of the problem as well.