The DK Rap uses samples from the Roland M-DC1 Sound Expansion Module.
There was a special edition Donkey Kong 64 controller released through Nintendo Power. Original advertisements showed the controller with the entire Donkey Kong 64 logo, but this was changed to only saying "DK64" by release.
If the player hacks their way back to Troff 'N' Scoff's room in a level where they have defeated the boss, the door will show a large "DK" with a green check-mark over it. It's possible this is a leftover of an unused way to go back to a room after a boss fight had been completed.
It's possible to access a test room without the use a cheat device. To do this, the player must have all of Snide's HQ blueprints, then bring up any level in the Bonus menu, highlight any of the mini-games, then press and hold B, and quickly press A. If done correctly, the player will be taken into the test room itself. The room has no music, three pedestals, a yellow balloon, and a motionless clone of Donkey Kong. It's not possible to leave the room, as pressing Start does nothing and going off-screen will take that player back to the room.
Early versions of the left and right trigger button icons can be found inside the game's code. These icons are much narrower than in the final game. They were mostly like widened to match the actual buttons on the controller.
An infinite life GameShark code increase the player's life melon count to 4, though the most you can have normally is 3. Even after disabling the code, your melon count will stay at 4. It's thought that Rare planned to implement an additional melon upgrade at Candy's shop. Alternatively, it's also possible that two melons were planned to be used at the beginning of the game instead of one.
A ROM was ripped from a demo kiosk version of the game, and was found to have three demo levels in it. They were the Army Dillo level, the Mine Cart level, and the Dogadon fight. Certain beta elements were in the ROM such as the silver balloon counter, Army Dillo's speech, and Dogadon's beta spit noise.
Using a glitch to get under DK Isle, going towards the waterfall will bring you to the escape ship cockpit King K. Rool used during the "K. Rool Press Button" cutscene.
The only reason the game needed the expansion pak was because it contained a game-breaking bug. The game would randomly crash in the 4 meg version, but when they installed the expansion pak it worked perfectly. Rare couldn't find any other solution, so they bundled the expansion pak with the game, costing them a lot of money. They still don't know what caused the bug.
"There was a bug that caused the game to randomly crash that only occurred in the 4meg-only version ... and they couldn't find out what it was, so they had to shift with the memory card in it for free and it cost them a fortune." - Chris Marlow
ASCII text for ICE KEY is present in the ROM. The Ice Key is one of the Stop 'n' Swop items in Banjo-Kazooie, so there may have been intended to be a connection between the two games.
Early screenshots of Donkey Kong 64 showed that Donkey Kong's Treehouse originally had a shower stall in it with a poster of Banjo and Kazooie on it.
Grant Kirkhope, composer for the game, provided the voice of Donkey Kong.
Despite being an E-rated game, the intro got away with mild swearing. Near the end of the song, the last line during Chunky Kong's portion of the song says, "But this kong's one hell of a guy". The game was developed by Rare, a British company, and in Great Britain the word isn't considered offensive. In later versions of the song the word is replaced with "heck".
The level Fungi Forest was originally a level from Banjo-Kazooie, another Rare developed game. The level was originally called Fungus Forest and the level can be seen in a picture at Banjo's house.
In Donkey Kong's cabin hangs a picture of a dolphin. This is a reference to the code name of the Nintendo Gamecube, "Dolphin". The game was released before the Nintendo Gamecube was revealed, and is thought to be the earliest reference to the code name "Dolphin."