Long story short, Mario Kart games also have metas of their own. (Doh!)
For those unfamiliar with the term, “meta” is a shorthand for “meta game”, meaning anything relating to how the game is played, yet not directly part of it. In most contexts this is referred as “the meta” to mean “the best strategy right now”. The term is commonly used for multiplayer strategy games. They tend to offer lots of different possible characters, items, strategies, and a couple of those will prevail over time and become the thing that’s generally the best.
This also happens, in a way, with games like Mario Kart. There may not be very much strategic depth, and items are more focussed on generating a rubber-band effect (allowing for those who have fallen behind to make an easy comeback), but there’s still a meta of sorts. And I’m not even talking about the karts best suited to most tracks, I’m talking mechanics here.
Some time after Mario Kart DS’s release, people discovered a technique that got dubbed “snaking”. It essentially “abused” a speed boost mechanic enabling skilled players to get a periodic speed increase, even on straight parts of tracks. As more and more people discovered this technique, the avid WiFi players picked it up as well. Soon, it became really hard if not impossible to win an online cup unless you also hopped aboard the “snaking” bandwagon. It had become a defining aspect of MK DS’s meta.
In conclusion, “the meta” isn’t just in characters or items, but can also be in mechanics, techniques and other “indirect” gameplay elements.