www.warioworld.com was an official Nintendo website made as a hub for developers and publishers licensed to work on Nintendo hardware. The site used Wario as a mascot, something that may not seem strange as his profession is designing video games in the WarioWare series. However, the site was opened in 1997, predating WarioWare by multiple years, and also predates the Wario World game for GameCube. Instead of renaming the site to avoid confusion and using the URL for the game's US promotional site, the URL www.wario-world.com was used for the game's website, something that more than likely caused confusion for Wario fans. WarioWorld was closed in 2016, having received very few visual updates since the 1990s, and now redirects to a more modern and professionally designed Nintendo developer hub.

The Japanese version of the game was released later than the Western release, allowing for Treasure to tweak some aspects of the game, the most notable being that Black Jewel has a second boss phase with completely new music. Black Jewel floats down to the arena where Wario must attack it until it gets dizzy so he can perform a Mad Move on it. Black Jewel also has new animations after each big hit it receives, retracting its arms and spinning as it glows.

Pausing and waiting 50 minutes will cause Wario to stop making the noises he usually makes and say "sorry" to the player.