It has been 19 years since Mario Kart DS first hit the tracks. That's a pretty staggering length of time and one that we'll probably need a little sit down to fully recover from. But hey, while we freak out about the passing of the years, check this out: speedrunners have found a handful of new shortcuts on the DS' previously pretty water-tight circuits (thanks, Gaming Reinvented).
The biggie here is on the Waluigi Pinball track where a shortcut that was previously discovered in tool-assisted speedruns (TAS) has been seemingly proven humanly possible by speedrunner iMathII. It's a tricky manoeuvre that requires the driver to hit a section of the spiral track just right, but if done correctly, the kart is hurled across a large portion of the circuit, landing by the pinball bumpers at the end of the lap. You can see it in action in the above video.
As it turns out, this move actually has its uses on a couple of different tracks too. Tool-assisted runs have already used a similar technique to skip long sections of the Luigi's Mansion circuit and speedrunner @MK_Dasher claims that it can be used on Delfino Square too.
These later examples appear to be only available in the tool-assisted realm at the moment, but if recent developments from the Mario Maker speedrunning community has taught us anything, it's that it will only be a matter of time before the pros are putting these shortcuts to the test.