If the game detects anything other than a control pad plugged into either port, an error message will pop up until the offending controller is removed. The color of the text changes every frame, gradually cycling through the entire 32,768-color palette.

The enemy "Burt the Bashful" looks like Obelix from "Asterix". This was referenced in other language versions of the game. The boss's name in the French version of the game is 'Belixo', an anagram of Obelix. In the German version of the game the boss's name is Xilebo, Obelix spelled backwards.

There are several unused enemies and enemy behaviors. The unused enemies include a Red Bullet Bill and Cannon, a double swap platform and a Bloo Blah holding a Piro Dangle. The unused enemy behaviors are Egg Plants spitting bubbles at a regular interval and three Cactus Jacks falling down and forming a stack.

When approaching the boss Naval Piranha, the player can see him in his un-transformed state and can fire an egg at him. Doing so results in him dying instantly, and Kamek flying in to yell "OH, MY!!!" before flying away in retreat.

An unused monkey enemy can be found in the game's graphics. They look to be similar to Donkey Kong in the style of Yoshi's Island, including a barrel that would have presumably been thrown.

There are a number of unused transformations in the ROM that never made it into the final game. These include a plane, a mushroom and a tree.

In May 1995, an interview with series creator Shigeru Miyamoto and Rare co-founder Tim Stamper about the development of Donkey Kong Country (DKC) was published in the magazine Electronic Games, conducted by game journalist Steven L. Kent. Kent later claimed on an episode of G4's docuseries "Icons" that Miyamoto was angry during this interview, channelling it into bitter criticisms of DKC's gameplay and the Western market's praise of its pre-rendered graphics, and that Stamper "sat there and took it, even though really the anger wasn't meant to be at Stamper". Miyamoto clarified in a 2010 interview with IGN that he did like the game despite these rumored criticisms, and that he worked closely with Rare and Stamper during development.

Years after the interview's publication, Kent would print an alleged portion of a later interview with Miyamoto in his 2001 book "The Ultimate History of Video Games", claiming that the anger had stemmed from "touchy" internal discussions regarding Super Mario World 2: Yoshi's Island. The hand-drawn crayon art style of that game was said to be a result of the alleged anger over DKC's graphics causing him to rebel against Nintendo's internal evaluation committee, who wanted Yoshi's Island to use pre-rendered graphics. Part of the Miyamoto quote reads:


Developers on Yoshi's Island have given less angered statements regarding the choice in art style over the years. Yoshi's creator Shigefumi Hino and game director Takashi Tezuka each claimed that it was done for sentimental reasons, as the development team believed that all video games from that point on would likely utilize 3D graphics. They decided to "fight back" in Hino's words by scanning in hand-drawn illustrations and manually editing them to be readable sprites, creating a unique art style intended as a bow-out for 2D graphics:


Since then, every game in the Yoshi series has taken on a deliberately different visual style, including hand-crafted assets and real-world materials, to set itself apart from the Mario series.

There's a part of the background in world 4-1 that appears to take the shape of a topless woman's torso.

In the German version of Yoshi's Island, Naval Piranha is named "Audrey", referencing the 1960 film "The Little Shop of Horrors".