Franchise: Banjo & Kazooie

A common belief relating to Rare's work with Nintendo in the 1990s is that the Banjo-Kazooie series and the early family-friendly iteration of the Conker series were originally intended to share a universe with Donkey Kong. By extension, this would also connect them to the Mario series. This belief stemmed from Banjo and Conker's debuts as playable characters in Diddy Kong Racing, other shared characters (e.g. Gnawty, a beaver who appears in both Donkey Kong Country and Banjo-Kazooie), and other planned appearances like the Ice Key from the Banjo-Kazooie series' unused Stop 'n' Swop feature being found in the data for Donkey Kong 64. This interpretation was so popular at one point that the largest English-language Mario fan wiki, Super Mario Wiki, hosted articles about Banjo-Kazooie and Conker characters.

However, Banjo-Kazooie creator Gregg Mayles has stated that Rare's non-Donkey Kong games were never intended to share a universe with Donkey Kong, while Conker's Bad Fur Day director Chris Seavor has gone on to say that Banjo-Kazooie and Conker also do not share a universe.

The Breegull Bash move in the Japanese versions of Banjo-Tooie and as well as Super Smash Bros. Ultimate is called ハリセンカズーイ(Harisen Kazui), which literally translated into English is "Slapping Fan Kazooie". A harisen is a giant paper fan that is typically used as part of a manzai act, where the straight man smacks the funny man in response to their jokes or foolishness. The "Fan" item that appeared in Super Smash Bros., Super Smash Bros. Melee, and Super Smash Bros. Brawl is actually a harisen, and it's even called as such (はりせん) in the Japanese version of those games as well.

It's worth pointing out that in general, the Japanese localizations for the Banjo-Kazooie games seem to exclude any mention of the word "Breegull", the name of Kazooie's species. This is something Masahiro Sakurai made note of when showcasing Banjo & Kazooie's moveset in Super Smash Bros. Ultimate.

A picture of Gruntilda from Banjo-Kazooie can be seen hanging in Professor Pester's lair in the episodes "Wild Horstachios" and "My Sweet Sour" of the Viva Piñata animated series.

A few characters throughout the series can be heard at times shouting "wahey", which is a British phrase used to express exhiliration or delight.

During the "Behind the Scenes of Banjo Kazooie" video in Rare Replay, the developers revealed that the decision to do garbled noises for each of the characters rather than full voice acting was due to time constraints, since recording so much dialogue would have greatly increased the development period of the games.

Gruntilda's name is based on an inside joke concerning the series' composer, Grant Kirkhope, where he'd be called "Grunt" instead of Grant. Gruntilda's surname, "Winkybunion", Spoiler: revealed during the final boss fight in Banjo-Tooie , is based off British slang for penis and wart, respectively. Despite this, the game was still given an E Rating by the ESRB. In addition, the development team would occasionally refer to Steve Mayles as "Winky Boy".

A Banjo-Kazooie game was in development for the Game Boy Color, under the name 'Banjo-Kazooie: Grunt's Curse'. It would have featured Gruntilda putting a curse on Kazooie, and carrying her in a backpack, similar to Banjo.
It's unknown why the game was canceled, but some of the ideas would later be reworked into Gruntilda's Revenge for the Game Boy Advance.

The Jinjo's name came from an in-house joke in reference to the game's artist Ed Bryan who was given the nickname 'Ging' for the fact of his ginger hair.