Originally released in 1999 for the Nintendo handheld, the game was shipped with hidden rumble functionality built-in, but didn't actually come on a Rumble Cart to enable people to experience it.
This information was briefly mentioned at the time in developer interviews, where Digital Eclipse's then technical director Mike J. Mika said it was cut due to being costly to manufacture, but it seems to mostly have been forgotten about in the decades since until Mika shared the piece of trivia again in 2021 alongside an image of a Game Boy Color development cartridge.
We were only made aware of it recently, however, thanks to a tweet earlier today, where Mika reacted to a video from a YouTuber named Zack G who had managed to get it working by flashing the game to an EZ Flash Definitive Edition cart (which includes a built-in rumble):
According to Mika, in an IGN interview from 1999, the game was initially designed to fully support rumble functionality throughout the entire game, but in the end, was only programmed to go off during specific encounters with wild boars and the villain Clayton.
If it had shipped, it would have joined a list of 23 other official titles released on a rumble cartridge for Game Boy Color, alongside games like Perfect Dark, Ready 2 Rumble Boxing, and Pokémon Pinball.
