When you collect a Mumbo Token, a sound effect of Mumbo saying "Ikkum Bokum" plays. This phrase (and most of Mumbo's speech aside from "Oominaka" and a few other sound effects) are all made up of randomly-arranged soundbites. When these soundbites are arranged in the correct order, they say "Come and have a go, if you think you're hard enough."

When Mumbo turns you into a creature he says "Oominaka." Grant Kirkhope, Mumbo's voice actor, revealed that at the time of recording the voices for the game his left testicle was swollen. "Knackers" is British slang for testicles, so he thought it would be funny if Mumbo said "Ooh, my Knackers." Thus, every time that Mumbo uses his magic to turn you into a creature, he's actually complaining that his testicles are in pain.

The music played inside the Ant Hill of Mumbo's Mountain is a slowed down version of what was originally intended to be the world's main theme. The original theme was partially inspired by the Baby Elephant Walk tune from the film "Hatari!".

The theme that was used for the world Treasure Trove Cove was also the second version that the game's composer, Grant Kirkhope, had written due to the change of the game from "Project Dream" to "Banjo-Kazooie".

Napper the Ghost and Clanker's voices are both Banjo's voice but slowed down and lowered respectively. This was done due to not enough memory space on the cartridge to add additional voices.

The idea behind "Stop 'N' Swop" was to do certain challenges/objectives in "Banjo-Tooie," then stop and swap the cartridges while the system was still on. This would have unlocked special items in "Banjo-Kazooie." You can than swap the games again to get the items in "Tooie." This idea was scrapped when the window of time that players could "hot swap" games (the ability to switch games when the power was on) was shortened from 10 seconds to only 1 second. There are still cheat codes that will unlock the special items in Banjo-Kazooie.

On the third file select, you can see Banjo and Kazooie playing a Game Boy. The sound effects coming from the Game Boy are from Donkey Kong Land.

On the title screen, there is a slight chance that you may get an alternate file select animation. These include Banjo being flipped out of his bed and out his window, the wall in Banjo's kitchen spinning around, and Banjo being launched out of his chair.

Banjo-Kazooie started development on the SNES and was titled "Project Dream" or "Dream: Land of Giants". The game was going to be an RPG, and the main character would have been a young man named Edison who had caused trouble with a group of pirates led by a man named Captain Blackeye.

A few of Banjo-Tooie's worlds were originally planned for its predecessor, Banjo-Kazooie, such as the fire side of Hailfire Peaks and Glitter Gulch Mine. Many of these were cut primarily because of time constraints.

Gobi mentions leaving for the "Lava World" in Click Clock Woods, which adds up as Gregg Mayles' concept art for the cut lava world shows that Gobi would have been present. Gobi would eventually live up to his promise by appearing in the fire side of Hailfire Peaks in Banjo-Tooie, after being freed in Witchyworld.