According to an Ask the Developer interview, the idea behind "NPC drivers" (playable characters that also appear in the game as background elements such as obstacles) came about after a designer drew a sketch of a cow from the Moo Moo Meadows course driving a car. This led art director Masaaki Ishikawa to realize the potential for using the course surroundings as playable characters, feeling they wouldn't look out of place in the game, and Cow was added as a racer alongside other characters like Cheep Cheep and Pokey. This also inspired the idea behind the Kamek item, which turns the racers into playable NPCs, and other obstacle characters built off the design of Cow such as Camel and Giraffe. Ishikawa would later joke that "Cow is actually a pivotal character in the Mario Kart series."

The idea of Mario Kart characters eating various foods and transforming into different costumes originally started as two different ideas. According to Mario Kart 7 and Mario Kart 8 director Kosuke Yabuki, the team almost considered having players buy costumes for specific characters using in-game coins (similar to the way players buy alternate-costumed characters in Mario Kart Tour), with players having to drive to a clothing store rather than the "Yoshi's" fast-food restaurant.

Additionally, the idea of characters eating food was already considered at the very beginning of development, but was nearly removed. According to general game designer Shintaro Jikumaru:

Development on Mario Kart World started as far back as when Mario Kart 8 Deluxe was just wrapping up production, and official work started at the end of 2017 as a title for the original Nintendo Switch. From the very beginning, the game started off as an open-world experience, which is why the game is called Mario Kart World instead of Mario Kart 9. Because of this, having 24 racers in a single game rather than 12, like in 8 Deluxe, was already in consideration.

Technical limitations of the original Nintendo Switch console made development very difficult, and the team shifted to the then-upcoming Nintendo Switch 2 in 2020. Because of the longer-than-anticipated development, the team released the Mario Kart 8 Deluxe Booster Course Pass to fill the void while Nintendo was still working on Mario Kart World.

A year after the release of Mario Kart 8, a hip-hop dance known as the "dab" would gain prominence in mainstream culture, becoming a popular internet meme. Mario fans later noticed that at certain angles, one of Donkey Kong's Jump Boost animations in Mario Kart 8 coincidentally resembled a dab, with Donkey Kong holding his head down and stretching out one of his arms, but keeping his other hand close to his head. In Mario Kart World, this animation returns in a different context. While Donkey Kong now faces his head forwards while doing the animation, straying away from dabbing, he also stretches out both arms, making the similarity to dabbing more prominent overall.

In the lead-up to the release of Mario Kart World, the official Mario Kart Facebook account made a post promoting it with the quote:


This is a reference to a stunt pulled in 2004 on the talk show "The Oprah Winfrey Show", in which Winfrey gave away new Pontiac G6 cars to her entire studio audience while repeatedly yelling "You get a car! You get a car! [...] Everybody gets a car!"