If there's ever been any fatal accidents in the history of Mario Kart, I'm sure the organization behind the kart tournaments is prepared by having plenty of 1-Up Shrooms at their disposal to revive any dead racers when necessary, because unless you're a generic enemy, non-recurring boss enemy or an important plot character for a one-off game or other such being across the Marioverse, you don't truly stay dead from my experience with the Mario franchise.