We often associate Pokémon Fire Red And Pokémon Leaf Green old cheat codes and duplication glitches, or hundreds of resets for a chromatic starter. Many players still think that a Mewtwo shiny necessarily requires Action Replay or emulator.
Good news: GBA cartridges like the Switch port hide a completely legal trick, the manipulation of the Pokémon RNG Fire Red Leaf Green. By finely controlling the internal random number generator, you can target almost any Pokémon without ever changing your save.
Pokémon RNG Fire Red Leaf Green: why is this tip not considered cheating?
The RNG, for Random Number Generator, is the sequence of numbers that the game uses for everything that seems random: encounters, IV, nature, shiny. In Red Fire Green Leaf, a seed is calculated at startup then advanced each frame. RNG manipulation is simply a matter of knowing which seeds yield which Pokémon, and pressing A at the right time. No code is injected, nothing is edited, you are just exploiting intended behavior.
Result: a Mewtwo obtained in this way is identical, to the nearest bit, to a Mewtwo fell by chance. Shiny hunter communities classify it as “full legit”. Conversely, ACE or cheat codes modify the ROM or the save, which is no longer the case here.
How to use Pokémon FireRed and LeafGreen’s RNG to target the ideal Pokémon?
It all starts with your secret ID, the SID, hidden behind the Trainer ID displayed on the Trainer card. To find it without cheating, you capture a Pokémon, note its nature, gender and statistics, raise it a few levels, then enter all this information into a Generation 3 IV calculator. With PokeFinder and the “IVs to PID” function, it is then possible to deduce your SID from these IVs and your Trainer ID.
Once the SID is known, you go to Ten Lines, a database of seeds tested for the Pokémon RNG Fire Red Leaf Green. You filter the species, nature, sex, shiny status and IV range, whether for a starter, Eeveea fossil or a legendary. The site then provides you with the precise timings to aim for, which you reproduce with EonTimer: a first counter for pressing A on the title screen, a second just before generating the Pokémon. Between each attempt, you must completely close the game to start from the same seed.
Which Pokémon can you get using Fire Red Leaf Green RNG manipulation, and who is it for?
Mastered, this trick opens almost the entire Pokédex: shiny starters, Mewtwo chromatic, legendary birds with good IVs, Eevee ideal or Dratini dreamed of fishing. On the other hand, aiming for several near-perfect pressures requires practice and a PC at hand.