With the exception of two worlds in Banjo-Tooie (Mayahem Temple and Witchyworld), all of the stage themes in Banjo-Kazooie and its sequel begin in the musical key of C (Major/Minor notwithstanding). Of the ten worlds in Banjo-Kazooie, including Spiral Mountain, six of the themes are in major, and four are in minor. Of Banjo-Tooie's nine worlds, again including Spiral Mountain, only three are in major, and six are in minor. This contributes significantly to Banjo-Tooie's darker tone, compared to its predecessor.
In Mad Monster Mansion in the original game, there's a piece of music on Motzand's giant organ in the chapel. If you happen to take out an instrument and play (or just sightread and whistle) the musical notes, you'll find that the tune represented is Mad Monster Mansion's level music. Particularly fitting, since the church's music itself is Mad Monster Mansion's music played by an organ.
Captain Blackeye, the pirate in Jolly Roger's Lagoon in Tooie, was one of the original characters of the game that became Banjo-Kazooie. The original game was entitled Dream; the game was initially for the SNES but the console was on its last legs and Captain Blackeye was an antagonist to the protagonist named Edison with a wooden sword. At one point Banjo and a dog were just secondary characters until Rare felt that Edison was too much of a generic character so they made the dog the main lead, then a Rabbit, and finally Banjo was made the lead character. That was referenced in Tooie, where Blackeye states he had a dream, and how a bear who looks like Banjo stole his glory.
The original game initially featured a full 15 worlds, but 6 were cut. Four of those, however, were eventually used in other games: The "lava world" that Gobi mentions was the original version of Hailfire Peaks (called Mount Fire Eyes then), eventually moved to Tooie. Fungus Forest eventually became Donkey Kong 64's Fungi Forest. An unnamed ore mine level became Glitter Gulch Mine in Tooie. Witchyworld was originally a stage in Banjo-Kazooie, but was removed and later re-added to Tooie.
Banjo-Kazooie and Banjo-Tooie were partially developed side-by-side. Because of this, some levels were traded around between the games prior to completion. Notably, Rusty Bucket Bay was moved from Tooie to Kazooie, and as stated above, Glitter Gulch Mine and WitchyWorld were both moved from Kazooie to Tooie because the developers believed both would benefit from longer development and the increased level size that became possible in Tooie.
Banjoland in Nuts & Bolts includes at least one exhibit from every level in the first two games. Some of the objects/exhibits appear in multiple levels in the original games, but they only tend to represent one in Banjoland. There are also additional miscellaneous props from the levels scattered around the level, but there is only one main exhibit surrounding each level. The primary exhibits are:
Stonehenge from Mumbo's Mountain
Captain Blubber's ship and a sunken treasure horde from Treasure Trove Cove
Clanker from Clanker's Cavern
A wooden statue of Tanktup from Bubblegloop Swamp
The (now melted) snowman from Freezeezy Peak
A pyramid from Gobi's Valley
Part of the mansion and several animate gravestones from Mad Monster Mansion
The Rusty Bucket ship from Rusty Bucket Bay
The giant tree from Click Clock Wood
A kickball field from Mayahem Temple
An ore pile and mine carts from Glitter Gulch Mine
The Cactus O' Strength from WitchyWorld
The UFO from Jolly Roger's Lagoon
Terry's nest from Terrydactyland
Loggo the toilet from Grunty Industries
Boggy's igloo from Hailfire Peaks
The mountain and the giant trashcan from Cloud Cuckooland
Banjoland, being a pseudo-museum, includes a number of signposts offering tidbits about each exhibit from the earlier games. Each of the signposts is numbered, with an apparent total of 20. However, there are only 19 posts in the level. The 20th, which would be #14 in the sequence, is supposed to be for Terry's Nest from Terrydactyland in Banjo-Tooie, according to the game files. Hacking has revealed that it is listed in the registry along with the other signposts, but the text has yet to be located, if it is in fact there to be found. One such signpost claims that Canary Mary's races originally required rotating the N64's control stick instead of rapidly tapping B, and that this was changed when the friction caused playtesters' palms to become raw. This is a joke in reference to Mario Party, which actually did have such challenges, in which players would use their palms instead of their thumbs to rotate the stick, indeed leading to scorched palms. While not confirmed, the Canary Mary challenges more than likely always used Button Mashing.
In Banjo-Kazooie's "Grunty's Furnace Fun" quiz challenge, one possible question was "What is on top of the Rusty Bucket's third funnel [a.k.a. smokestack]?" The answer was that the ship has no third funnel. In Banjoland, it suddenly has - you guessed it - three funnels.
Early in the development of Nuts & Bolts, Mumbo's Mountain from the original Banjo-Kazooie was planned to potentially make a returning appearance as its own level, similar to what happened with Spiral Mountain. Grant Kirkhope, the composer for the series, created a 4-minute orchestration of the classic Mumbo's Mountain theme for use there. The level was cut long before the game began solid development however, and the song went unused in-game, instead appearing in the original teaser trailer and one additional later trailer. The full piece is still present in the game files.
On the subject of cut music, in the original game there's the infamous "Advent", an unfinished-sounding piece that sounds utterly unlike anything else in the game. There were quite a few fan theories as to what the damn song was actually meant for, but the most popular was that it was for the cut level Fungus Forest, presumably due to its similarity to the music for Fungi Forest in Donkey Kong 64, at least in terms of instrumentation. Rare has officially confirmed that it was for the Giant's Lair (see below); this can be confirmed by what little music can be heard (i.e. behind commentary) in early footage of the Giant's Lair. (Note that Grant Kirkhope has confirmed that the proper name of the song is "Adventure", which is a name more fitting of a hub world theme; the name "Advent" is a result of the filename being truncated.)
The rock remix of the B-K theme heard in the Nuts & Bolts trailers was based on a similar arrangement heard on a radio in Rare's earlier title Kameo: Elements of Power. The full version is present on the N&B game disc, but is not used anywhere in the game, much like the Mumbo's Mountain theme mentioned above.
Prior to the release of Banjo-Kazooie, a promotional VHS tape was distributed showcasing video clips of an early build of the game, with a narrator describing each world. In describing Rusty Bucket Bay, the narrator incorrectly gives the name of the ship as the HMS Gruntilda, when both Banjo-Kazooie and Banjo-Kazooie: Nuts and Bolts give the name as simply the Rusty Bucket. This also carries the implication that the ship is part of the British Royal Navy, which it clearly is not.
In Grunty Industries, there are numerous crates that say they are bound for Twycross, England. Twycross is a civil parish in Leicestershire, and is where Rare is based. Both the BK and BK:N&B versions of the Rusty Bucket list Twycross as their home port; an oddity considering Twycross is completely landlocked.
The chanting in the music that soundtracks Tooie's Mayahem Temple level sounds like Mumbo's usual gibberish, but if you listen carefully, you realise that it's actually saying "Come and have a go, if you think you're hard enough". This is a popular term often associated with football in the UK, appropriately enough for the level's kickball elements, and was inserted by composer Grant Kirkhope as a joke.
The first game's ending originally had the lady in the bikini carrying cocktails on a tray and sporting breasts larger than Nintendo was comfortable with, so the size of her breasts was reduced and the cocktails were replaced with melons.
Pulled these for not being hooked to a trope.
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