In the Spanish Official Nintendo Magazine, a picture was shown that included Diddy Kong in the cast of characters, suggesting that he was a planned character for the game, but was cut. Diddy Kong would later be included as one of the last four characters for the Deluxe port’s Booster Course Pass DLC, nearly a decade since the original game’s launch.

An unused emblem for Kamek (or an unnamed Magikoopa) appears within the original Wii U version's files, suggesting he was intended to be a playable character at one stage during development. Kamek would later be added as a playable character in Wave 5 of Mario Kart 8 Deluxe's Booster Course Pass DLC.

In version 1.1, one of the Inkling Girl's gestures was altered, as the original animation could have been interpreted as an offensive gesture in certain cultures.

Although they remain uncredited, Bandai Namco contributed to the development of Mario Kart 8 Deluxe, Mario Kart Tour, and Arms.

In the Booster Course pack (as well as the track's appearance in Mario Kart Tour), the advertisement for Barrel Travel in Coconut Mall has barrels which use the exact same sprite as they do in Donkey Kong.

The Koopa Troopa shell bouncing between the pipes of the starting gate to Wii Koopa Cape (a course included in Tour and Deluxe's Booster Course Pass DLC) is a reference to a Koopa Troopa's behavior when Mario/Luigi jump on, kick, or throw a stepped-on shell.

The ring seen in the drain portion of Squeaky Clean Sprint resembles the Binding Band from Tostarena in Super Mario Odyssey.

The racers may have planned to have losing animations for when they reach 5th or lower. In the game's data are Peachette and Pauline's losing voice clips, as well as voice clips from characters that appear in Mario Kart 8 Deluxe (prior to the Booster Course Pass). The final game has the racers appear neutral should the player end up in 5th place or lower.

Since Pauline and Peachette were included as among two of the final four characters in the Booster Course Pass, these unused voice clips may have been a deciding factor behind their inclusion in Mario Kart 8 Deluxe.

Prior to the official announcement of Yoshi's Crafted World's title, a fake leak was posted on 4chan listing off future Nintendo games, containing the title of Yoshi's Crafted World. This leak was humorous in nature, contrasting legitimate sounding titles such as Animal Crossing: Town Founder and Paper Mario: Clay Catastrophe with obvious jokes such as Metroid: Equestrian Races and Rhythm Heaven and Hell. This led to a short-lived theory that the leak was indeed real and slid in the joke names for humorous effect. Over time, reveals of installments in other franchises featured in the leak that didn't line up would show that Crafted World was simply a lucky guess. However, some other articles from the leak, such as a multi-part DLC pass for Mario Kart 8 Deluxe, Pokémon Diamond and Pearl remakes, a Tokyo 2020 Mario & Sonic Olympics game (albeit without Pac-Man), a Switch port of Overwatch, and the at-the-time-believed-to-be-cancelled Pikmin 4 would come into fruition later by coincidence.

Aside from the RMX stages that appear in the original game, Piranha Plant Pipeline is the only Tour stage absent from Mario Kart 8 Deluxe's Booster Course Pass DLC. This was most likely done as a way to avoid confusion with the pre-existing Mario Kart 7 stage Piranha Plant Slide, which contains many similarities to Piranha Plant Pipeline.

Piranha Plant Cove (included in Mario Kart Tour and Mario Kart 8 Deluxe's Booster Course Pass DLC) is the only non-city Tour course that has more than one layout.

As a throwback to the original Mario Kart Wii version, if the player falls off the Wii Rainbow Road stage included in the Booster Course Pass DLC, the character and kart will burn as they briefly enter the Earth’s atmosphere before Lakitu rescues them. This marks the only stage in the entire game (including the original Mario Kart 8) that has this property.