Donkey Kong Country Returns
Wii Cameos
Foggy Fumes
The Foggy Fumes levels contains several blink-and-you'll-miss-it cameo appearances in the background.
25M
Near the start of the stage, you can see a construction site in the background laid out exactly like the 25M stage from the arcade Donkey Kong.
Mr. Game & Watch
Around halfway through the stage, you see Mr. Game & Watch, the representative of the Game & Watch systems. He is hammering on a pipe in a simple 2-frame animation.
Crocomire Skull
You can see a crane in the background, lifting a large object filled with holes. The shape is the same as the skull of Crocomire, a miniboss from Super Metroid.
Submitted by MEGAߥTE, Da Robot, The Qu
Wonky Waterway
Donkey Kong Arcade Temple
Near the beginning of the Wonky Waterway stage, the entrance to the temple is blocked by huge stone blocks sporting the face of Donkey Kong as he appeared in the original arcade game.
Donkey Kong Jr. Math Statue
Towards the end of the level, in the background you can see a giant 8-bit statue of Donkey Kong holding up a Wii remote. The sprite has been modified, but it originally came from Donkey Kong Jr. Math.
Submitted by Fryguy64, Da Robot
Donkey Kong's DS
If Donkey Kong is standing on flat ground and you don't touch the controls for a while, he sits down and pulls out a white Nintendo DS Lite and plays with it for a few seconds.
Submitted by MEGAߥTE
King of Cling
Stage 1-2 is named "King of Cling", which is a reference to the title of DK: King of Swing (GBA).
Submitted by The Qu
Donkey Kong Jr. Music
The final stage in the game, the Golden Temple, is only unlocked after you collect all the KONG Letters and the Orbs from the temple stages in each world.
The music in the stage is a remix of all of the music from the Donkey Kong Jr. arcade game.
Submitted by MEGAߥTE
Billy Mitchell
At the very beginning of Stage 3-2: Button Mash, head to the right and jump into the first Barrel Cannon. The giant stone monkey on the right is wearing a tie featuring the stars and stripes of the American flag.
This is the iconic tie worn by Billy Mitchell, the world record holder for the Donkey Kong arcade game.
Submitted by MEGAߥTE, original discovery by Lijik on NeoGAF
Factory Diorama
When you collect the Diorama for the Factory world, it is laid out similarly to the 25M stage in the arcade Donkey Kong. Donkey Kong stands at the top, preparing to throw a barrel, while other barrels are rolling down the girders.
Submitted by ville10
Concept Art Cameos
Concept art for the game has shown a number of elements that didn't appear in the final game. Some of this concept art can be unlocked in-game, while others have been released on the internet. Several of these feature cameos:
Virtual Boy Minecart Stage
Concept art shows a Minecart stage set in a red and black level inspired by the Virtual Boy.
Virtual Boy Super Mario Bros. 2 Stage
Another black and red Virtual Boy stage appears to have been inspired by Super Mario Bros. 2.
Factory Hardware Stage
One piece of concept art shows a huge structure made out of pipes and bits of machinery. Look closely, and you can make out buttons and controller ports from a variety of Nintendo hardware, including the NES and Super NES.
Kraid
One piece of concept art shows a rocky structure that appears to be in the shape of Kraid, the giant reptilian boss from Super Metroid.
Submitted by The Qu, Fryguy64