Pokemon FireRed/LeafGreen Secrets (GBA)

Catch Mewtwo: Beat the Elite Four, then go to Cerulean Cave.

Catch Zapdos: Find it in the Power Plant.

Catch Articuno: Find it in Seafoam Islands.

Catch Moltres: Find it at Mt. Ember on One Island after getting the National Pokedex.

Get the National Pokedex: Catch at least 60 Pokemon, then talk to Professor Oak.

Unlock the Sevii Islands: Defeat Blaine, then Bill takes you to One Island.

Unlock Ruby/Sapphire Trade: Complete the Sevii Islands Ruby and Sapphire gem quest.

Get a Diploma: Complete the Pokedex (catch all 386 Pokemon) and talk to the Game Designer in Celadon City.

Duplicate Rare Candy: (Glitch) Save in front of PC, deposit Pokemon holding item, change boxes (DO NOT save), reset. Item will be on Pokemon and in PC.