If you want to change that Pokemon with your favorite Pokemon, RB Tilescreen Editor will be the most suitable tool for you.
RB Tilescreen Editor
Platform(s): GB Hack Tools
Type: Miscellaneous
Compatible with: Pokemon Red, Blue
Supported OS: Windows
Type: Miscellaneous
Compatible with: Pokemon Red, Blue
Supported OS: Windows
RBYG Trade Editor
Use the RBYG Trade Editor and you can trade anything you want to get a Pokemon and vice versa.
Type: Miscellaneous
Compatible with: Pokemon Red, Blue, Yellow, Green
Supported OS: Windows
RHEA
ROM Header Editor Advance (RHEA for short) is very helpful when you want to edit the ROM header.
Type: Miscellaneous
Compatible with: Pokemon Ruby, Sapphire, Emerald, FireRed, LeafGreen
Supported OS: Windows
Pokemon Intro Editor
After bypassing the main title by presisng the Start button, you will get to the intro of Professor Oak’s intro.
Type: Miscellaneous
Compatible with: Pokemon Red, Blue
Supported OS: Windows
Pokemon Titlescreen Editor
Pokemon Titlescreen Editor has the same functions like RB Titlescreen Editor, which means you can edit the Title of the Pokemon game you are going to hack.
Type: Miscellaneous
Compatible with: Pokemon Red, Blue
Supported OS: Windows
PokeTronic
With PokeTronic, you can edit the currently existing wild Pokemon events.
Type: Miscellaneous
Compatible with: Pokemon Ruby, Sapphire, Emerald, FireRed, LeafGreen
Supported OS: Windows
Free Space Finder
If you do not have enough free space in the ROM you want to hack, that will be impossible.
Type: Miscellaneous
Compatible with: Pokemon Ruby, Sapphire, Emerald, FireRed, LeafGreen
Supported OS: Windows
NarcExplorer 2
To edit and hack the narc files, you need to have the NarcExplorer 2.
Type: Miscellaneous
Compatible with: Pokemon Diamond, Pearl, Platinum, Heart Gold, Soul Silver, Black, White
Supported OS: Windows