The Cursed Cart is a corrupted DKC cartridge that was given to me by a roommate back in 2012. He said that it was purchased normally and that him and his brothers played it for a while with no problem until it eventually stopped working.
The cartridge has a plethora of weird effects, but the most notable one is the ability to hover while holding X, which I believe to be some sort of beta function that was disabled in the final release. (I've tweeted at some ex Rare devs about this, but haven't received a response yet).
When you attempt to play the single player mode in this game, it's extremely buggy and crashes nearly everywhere. When I first discovered how to stop the game from crashing immediately, I was able to find a way to beat single player, but it has since corrupted further and that is no longer reasonably possible. (There IS a way I found once, but I have since been unable to replicate it).
However, one of the many things I tried (on my stream viewers' suggestion) was the two player modes. It just so happens that, while Two Player Team is the same, Contest allows all of the levels to be played without problem. The only persistent bug in this mode is the inability to play Diddy. If you happen to get hit and lose Donkey, the game will actually crash upon touching a DK barrel, rendering the game impossible to complete, as there are several unavoidable ones.
Despite being able to fly over everything, it is actually fairly difficult to not get hit at all, especially during the cave levels, which makes this a fun and extremely silly speedrun.
I have read about this phenomenon elsewhere on the Internet, and have actually found another corrupted DKC cartridge at MAG once, though it was before discovering the ability to fly in this one, so I sadly didn't check for that. So I have never personally seen another flying cartridge.

You can watch my attempts to speedrun the cursed cartridge on my Twitch channel at http://twitch.tv/newageretrohippie
There are also videos of it being completed on my youtube channel at http://youtube.com/hippiesrl