Nintendo tends to launch one Mario Kart game per console, hence the hope that the Switch will be getting a Mario Kart 9 being squashed multiple times already. That didn't stop one studio from attempting to partner up with Nintendo in 2004 by pitching Mario Kart XXL for the Game Boy Advance, three years after it had already launched what wound up being the only MK title on the console, Super Circuit.
Very little is known about Mario Kart XXL and although snippets of information have found their way online in recent years, Forest Of Illusion (thanks, Nintendo Life) recently came into possession of its tech demo. Presumably the same tech demo its creators showed Nintendo in an attempt to get the game off the ground. Hard4Games has showcased that demo on YouTube and as you can see, it's pretty different from any Mario Kart game that came before it.
In fact, it's pretty different from any Mario Kart game full stop. Although the camera can be zoomed in so you're right behind the somewhat crude Mario design, the feature that sets XXL apart from other games in the series is the ability to zoom out. Not only might that let you see what's ahead in a full and polished version of the game, but you'd also have been able to scout out where your opponents are, including anyone creeping up behind you.
Denaris Entertainment Software is the studio responsible for the demo, and as you will have already deduced since XXL nor any Mario Kart game like it exists, the pitch failed. DES did go on to make a kart game for the GBA, though. Crazy Frog Racer. As demonstrated at the end of the video above, it's probably for the best the studio didn't get the chance to move forward with its Mario Kart game, although Nintendo's budget would have been far bigger than the one offered up by whoever owns the Crazy Frog IP.
If you want to get a feel for the Mario Kart game that never was, you can download it now through Forest Of Illusion. If you want to stick to Nintendo-approved games, there are more waves of DLC tracks coming to Mario Kart 8 Deluxe soon.