What is Donkey Kong 64's most hidden collectable?

Donkey Kong 64 already was seen as a game with a huge amount of collectables, but after the discovery of a new rainbow coin in 2017, the community wondered what else was lurking inside the game. Let's explore this idea.

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MUSIC
A mysterious sighting:    • Pokémon Snap - A Mysterious Sighting  
Cheato's Theme:    • Видео  
Snide's HQ:    • Видео  
Disco Zombie:    • Earthworm Jim 3D (PC Version) OST - D...  
Wizards and Lizards:    • Видео  
Snow Worries:    • Ty the Tasmanian Tiger OST 'Snow Worr...  
Cortex Vortex:    • Видео  
Angry Aztec:    • Видео  
Professor Layton's Theme:    • Видео  
75m Remix:    • Donkey Kong - Remix -  

CHAPTERS
0:00 - Introduction
0:46 - Defining a collectable
1:23 - Test Room Balloon
2:32 - Chunky Galleon Out-of-Bounds Coins
3:14 - Diddy's Mountain Coloured Banana
3:37 - Tiny's 5-Door-Ship Coloured Banana
3:55 - DK's Japes Out-of-Bounds Coloured Banana
4:39 - Hidden Caves Beetle Race Golden Banana
5:47 - No Logo Stealthy Snoop Golden Bananas
7:33 - Conclusion