actually you can't some pokemon evolve when they are happy enough,so you will understand.You can rises your pokemon's happyness by haircutting it at the UNDERGROUND,at Goldenrod City.
Easly
In Pokemon Crystal.
What the hell is a Pokemon crystal
You can't find Charizard in Pokemon Crystal. You have to trade it from Pokemon Red, Blue, or Yellow.
There is no Groudon in Pokémon Crystal.
You can find it in Pokemon Platinum, Pokemon Crystal, Pokemon HeartGold, and Pokemon SoulSilver.
You cannot find Squirtle in Pokémon Crystal.
you find all the Pokemon
There is no such thing as a Crystal Onix in the Pokemon games series. It was only in the Pokemon anime.
you will find it north to cherrygrove, on route 30
above the bike shop in goldenrod
You could get a shiny Pokemon for crystal but you need luck to catch one ("_")