Pokemon Firered & Leafgreen

Pokemon Firered & Leafgreen are two Game Boy Advance games of the third generation of Pokemon.

Version-exlusive Pokemon
There are some Pokemon that are only in one perticular version. These are most of them.

Hacks
There are some infamous hacks of Firered & Leagreen.

Pokemon ChaosBlack
The most famous Firered/Leafgreen hack the mascot resembles Chaos from the Sonic series.

It is unknown if Chaos himself is the mascot. This game featured unofficial, yet new Pokemon. Most of the Pokemon resemble Pokemon from the Ruby & Sapphire hack, Pokemon Quartz.

Pokemon: Special Sonichu Edition
Another infamous Firered/Leafgreen hack. This is the first and only appearance of Sonichu and Rosechu in the Pokemon series.

Sonichu & Rosechu are the only (possibly) starter Pokemon in this game (even though there is a third ball on the table, for some reason).