Donkey Kong 64

Donkey Kong 64 is a 3D platform game in the same vein as Rare's earlier Banjo-Kazooie, only supersized.

Stop n' Swop Connection
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.

Unused Fourth Melon
During normal gameplay, it is only possible to extend your health to three melons. By using the Infinite Health GameShark code, the life bar will show four melons. Disabling the code will remove infinite health, but the melons will be kept. It is likely that Rare originally planned another melon alongside the instrument upgrade inside Candy's Shop in Gloomy Galleon or Creepy Castle, but the upgrade was scrapped. Alternatively, it is possible that two melons were planned to be used at the beginning of the game instead of one.

Unused Button icons
Narrow L and R controller button icons. The final game uses much wider icons.

Testing Room
A hidden testing room can be accessed by using a code in Snide's HQ. After collecting all the Blueprints, go to any Snide's HQ in any level and bring up the Bonus Menu. Highlight any of the mini-games, then press and hold B and quickly press A. If you did it exactly right, you won't be taken to the mini-game, but instead a strange room.

The room has no music, three pedestals, a yellow balloon, and a motionless clone of Donkey Kong. There is no escape from this room: if you walk off into the dark space beyond the borders, you will appear to exit the room but will reappear back inside of it again.

Pressing Start also does nothing, so exiting the level is impossible without turning the game off.

Bosses: The Main Event
CODE: 8074453E 0007 In the boss select in the Mystery menu, there is an unused option to select the boss fight against King K. Rool. It was probably removed because anyone can just go back and fight K. Rool again through the Flying Krock on DK Isle, making this option redundant. Unless you delete the save slot with the K. Rool battle, in which case, tough luck.

Cheats: Debug Pos
CODE: 80744540 0007 In the Cheats selection, there is another unused item, called "Debug Pos". Unfortunately, turning it on doesn't seem to do anything...

Troff 'N' Scoff Complete
CODE: 817444E6 002A (Enter any doorway in any level. Note that it will change depending on what level you are in.) If you hack your way back to Troff 'N' Scoff's room in a level where you have defeated the boss, the door will show a large "DK" with a green checkmark over it. Perhaps there was once a way to go back to this room after the boss fight has been completed? Most likely, this was an old method for boss rematches. The door won't open, even if the right Kong is out (though if you manage to hack past the door, it just goes to that world's boss), so the only way to exit the room is to select "Exit Level" from the pause menu (be sure to deactivate the code first).

There is also data for a Troff 'N' Scoff room in DK Isles. The amount of bananas needed to open it is 000, but it can't be opened. Trying to go through the boss door crashes the game, but since the "DK" with the checkmark appears after King K. Rool is defeated, it's safe to assume it's for that.

Snide's Flowers
CODE: 817444E6 000F (Use in DK Isles for desired effect; the room won't exit properly) In Snide's HQ, where the Golden Bananas are stored, there is a small bunch of flowers with grass for some reason.

The Mermaid's Coconuts
In the Mermaid's room in Gloomy Galleon, there are two inaccessible Crystal Coconuts beneath her throne. These can be seen using the "Swim Through Walls" glitch.

Fungi Forest Hub: The Closed Door
In the Fungi Forest Hub, there are three wooden doors. One opens to reveal a Banana Fairy. Another opens to reveal a Chunky Pad. The third door, however, remains closed. There is a small area inside that shows there may have been something for this door at one point. But, despite numerous fan theories to the contrary, there is no way to open this door.

Frantic Factory: Hidden Triangles
In Frantic Factory, there are two yellow triangles hidden under the pathway to the right of the world entrance.

Unused Animations
Many character have animations that would not otherwise be seen, but can be through hacking:
 * Tiny Kong Picking Up Barrels - Tiny never goes into any areas with barrels, so her animations for picking them up and throwing them go unused. Because she has the least physical strength of the Kongs, her throw is very weak. Interestingly enough, Tiny has a voice clip used exclusively for this unused animation.
 * Rambi Dogpaddling - Rambi never goes near water, but if he does, he has a dogpaddling animation at the ready.