Uploaded January 2026 | Updated September 2026, 3 weeks ago
Here is my first build unlocking the extra Game boy Color characters that are normally only available by transferring them over from the Game Boy Color game or importing a save file that includes them. These players are permanently unlocked in the ROM and customized to be playable against/with the standard characters in the retail game. Every player has unique stats and abilities.
Kate & Nina's outfits have been forced to be their standard ones because for some reason the game will make the 2 players on the right of the menu have their alternate outfits. That effect has been overridden for an accurate experience with the players appearances.
An additional hack I made was to give the GBC players the option to be left handed on the fly, which was only normally possible to choose when you create them originally for the first time on the GBC version of the game. Press and hold "L" just like you would for a normal player to be left handed when you select them.
The remainder of the retail game is unlocked as well including DK Jr and Shyguy, every court unlocked, as well as all extra features with the retail roster having "star" ability, MAX difficulty for CPU players unlocked, etc. You can erase the game to clear gameplay data and everything will still be unlocked and the GBC players still there.
Playing this ROM hack requires a 4MB RAM expansion pack for an N64 console, or needs as well to have the settings in an emulator changed to 8MB to allow the extra RAM to be usable.
This is a link to download the patch to update the retail ROM of Mario Tennis that you need to provide yourself. The ROM must be in a .z64 file format. This is a BPS patch file to be used with a ROM patching program. I created the patch file with a program called Beat.
drive.google.com/file/d/1jR51U9D1oMHkQUaZqTerFQ-Bl_wPhpSw/view?usp=sharing
Here is a great online patcher from romhacking.net that will work for this.
romhacking.net/patch
Thank you so much for playing and please leave comments with any questions or feedback!
Here is my first build unlocking the extra Game boy Color characters that are normally only available by transferring them over from the Game Boy Color game or importing a save file that includes them. These players are permanently unlocked in the ROM and customized to be playable against/with the standard characters in the retail game. Every player has unique stats and abilities.
Kate & Nina's outfits have been forced to be their standard ones because for some reason the game will make the 2 players on the right of the menu have their alternate outfits. That effect has been overridden for an accurate experience with the players appearances.
An additional hack I made was to give the GBC players the option to be left handed on the fly, which was only normally possible to choose when you create them originally for the first time on the GBC version of the game. Press and hold "L" just like you would for a normal player to be left handed when you select them.
The remainder of the retail game is unlocked as well including DK Jr and Shyguy, every court unlocked, as well as all extra features with the retail roster having "star" ability, MAX difficulty for CPU players unlocked, etc. You can erase the game to clear gameplay data and everything will still be unlocked and the GBC players still there.
Playing this ROM hack requires a 4MB RAM expansion pack for an N64 console, or needs as well to have the settings in an emulator changed to 8MB to allow the extra RAM to be usable.
This is a link to download the patch to update the retail ROM of Mario Tennis that you need to provide yourself. The ROM must be in a .z64 file format. This is a BPS patch file to be used with a ROM patching program. I created the patch file with a program called Beat.
drive.google.com/file/d/1jR51U9D1oMHkQUaZqTerFQ-Bl_wPhpSw/view?usp=sharing
Here is a great online patcher from romhacking.net that will work for this.
romhacking.net/patch
Thank you so much for playing and please leave comments with any questions or feedback!
