In the Mario Kart series, a wide selection of Racers are available to choose from. Although there was only eight in the first game, Super Mario Kart, the number of characters has increased throughout the series. Cool new racers are added to almost every installment after Super Mario Kart, and some are not included later on in the series.
The Mario series isn't the whole contributor to the lineup of racers, although it does offer a lot of them (because it is MARIO Kart, of course!). Racers can range from the DK series, the Animal Crossing series, the Pac-Man series, and even the Tamagotchi series!