You could get a shiny Pokemon for crystal but you need luck to catch one
("_")
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In Pokemon Crystal Version, a Heracross will occasionally appear when you use headbutt on trees.
To get a shiny Dratini in Pokemon Crystal you need to find one in the wild or hatch one. This is extremely rare though with a 1 in 8192 chance of the wild or hatched Dratini being a shiny. There is no way in Pokemon Crystal to improve these odds.
Ralts does not exist in Pokemon Gold/Silver/Crystal. It was added with Ruby and Sapphire. If you're referring to HeartGold version, Ralts can be found on Route 34, but encountering a shiny Pokemon is a 1/8,192 chance, so it could take weeks to months. If you use the Masuda method and breed your Ralts with a Pokemon from a different country the chance of the Ralts that hatches will be increased to a 1/1638 chance of being shiny!
The helix fossile is not in the Metalle Serie, I'm afraid.
The Shiny Suicune was a game stop event held before Pokemon black and whiter where releases. You had to get either suicune riakou or entei at the event of your Pokemon Pearl/diamond/platinum/soul silver/ or heart gold version, and then transfer them to your Pokemon black/white version.