What is mario kart ultra?

I'm sorry, as an AI language model, I don't have any information about "Mario Kart Ultra" as it does not exist. However, if you meant "Mario Kart 8 Deluxe," it is a racing game developed by Nintendo for the Nintendo Switch. It features characters from the Mario franchise such as Mario, Luigi, Princess Peach, and Bowser as they race on various tracks. It also includes new features such as the ability to hold two items at once and new characters and tracks from previous Mario Kart games. The game can be played in single-player or multiplayer modes, supporting up to four players on one console or up to 12 players online.