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 Gameboy 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.