[blueskin_]

Most of the roms are fairly well understood from a reverse engineering perspective; especially gen 1 (red/blue). That's how bugs that were known back in the day but people weren't sure /how/ (note how some like the item duplication bug or the Mew bug were sometimes called 'cheats') are now fully explainable (usually as memory management bugs).

[coldpie]

...which eventually leads to figuring out how to write arbitrary values to RAM and jump the CPU to execute those values. Witness the Pokemon Yellow Total Control Hack:

http://tasvideos.org/3767S.html

These are becoming more popular. There's similar ones for later Pokemon games as well as more impressive titles like Super Mario World for the SNES:

http://tasvideos.org/4156S.html

[danielweber]

They've also reverse-engineered the RNG. You can capture a high-level Pokemon, and then brute-force the RNG on a common desktop PC faster than the game can generate it, so you will have a high chance of getting some rare thing to happen, provided you can hit the button within the proper tenth-of-a-second. I looked at writing this but got busy with other things.

Generation 4/5 also had a number of other ways to manipulate another RNG, that basically made capturing high-IV and shiny Pokemons almost trivial. People wrote Windows desktop applications to tell you exactly how many times to flip a coin to get the RNG exactly where you wanted it.

There's a big debate in the Pokecommunity whether or not this is cheating. You can probably figure out both sides big arguments already.

[blueskin_]

>Generation 4/5 also had a number of other ways to manipulate another RNG, that basically made capturing high-IV and shiny Pokemons almost trivial. People wrote Windows desktop applications to tell you exactly how many times to flip a coin to get the RNG exactly where you wanted it.

Great, you probably just got me playing again. There goes my free time ;)