In Pokémon LeafGreen, key items can be found throughout the game, but one of the most important is the Fame Checker, which you receive from an NPC in the Pokémon Center in Celadon City. Other key items, like the Bicycle, can be obtained from the Bike Shop in Cerulean City after you have enough badges. Additionally, some key items are hidden in various locations, requiring exploration and interaction with NPCs.
You cannot get the Eon Ticket in Pokemon LeafGreen since it's a key item that is only available for Ruby, Sapphire and Emerald.
You can get Eevee in the topmost room of the back of the building where you get the key item TEA.
it is a key item that is used to progress into the story, you find it within the safari zone, once you find it return them to the safari warden. hope this helped :)
The Special Key is a key item in Pokemon Diamond. You can find this item in a warehouse in Veilstone City.
it's in the instruction booklet
You will find the key to the Gym of Cinnabar Island, From the Pokemon Mansion that is on the same island.
You have to find the key in the abandoned mansion.
You will need to work your way to the basement in the Pokemon Mansion, you will then find the Key.
The secret key is hidden in the basement of Pokemon Mansion which is located on Cinnibar Island.
The key to the gym
You need to get the TEA key item first from a old lady in celadon mansion then you'll be able to go in and out as you please.
you get it by searching for it for yourslf