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

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

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:


Yoshi's Island director Takashi Tezuka would deliver a less angered statement that may be related to these claims in a September 1995 interview with the magazine Dengeki Super Famicom. He claimed that the choice in art style was done for sentimental reasons, as the developers believed that all video games from that point on would likely utilize 3D graphics, and wanted Yoshi's Island to be a bow-out for 2D graphics:

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.

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.

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.

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.

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.

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.

In the Game Boy Advance version of the game, dying enough times during the intro level to get a game over will result in the game's save file displaying "World 0." This is the only time this icon is accessible in the game, and in any version of the game, as the Super Nintendo original gave you infinite lives to beat the tutorial level.

Inside the game's data is an unused and alternate sprite for Yoshi spitting watermelon seeds. The sprite is not as puffed up as the sprite in the final version.

In the game's ROM, empty levels slots are filled with copies of World 1-1. These slots can be accessed through the use of hacking tools. When one of these levels is accessed in the Japanese version, a special title card will be shown which translates to "Yoshi's Island - Hollow Grassland".

In "World 6 - Extra" in the Japanese release, Yoshi's name is spelled out as "Yossy" during the segment in which the player must jump on a number of moving platforms. This was changed in the International version to spell out "Yoshi".

The German version of the level "Touch Fuzzy, Get Dizzy" is titled "Lustiges Sporen Drama". This abbreviates to "LSD", referencing the psychedelic, disorienting effects of touching the Fuzzies that serve as the level's English namesake.

In stage "Extra 3: More Monkey Madness", a 21st Red Coin can be found. The coin is hidden under a peg occupied by a gray Tap-Tap, with a rotating Paddle-Wheel above it, making it difficult to access. In the Game Boy Advance port, this coin is removed, indicating that it may have been present in the SNES version due to either a glitch or mistake.

The enemy "Harry Hedgehog", a fast moving blue hedgehog, is thought to be a subtle reference to Sonic the Hedgehog.

It's possible that Tweeters were originally going to appear in the game. Tweeter graphics from Super Mario All-Stars appear in the game's code, and could have been place holder graphics for the enemy.

The North American commercial for the SNES version featured a man at a restaurant eating enough food to literally explode. This is a reference to the Mr. Creosote sketch from the 1983 movie "Monty Python's The Meaning of Life."

In a 1995 interview with Shigeru Miyamoto published in the September issue of Haou magazine, he was asked about how long it took to develop the game? He responded:

According to Plok co-creator Ste Pickford, Mario creator Shigeru Miyamoto considered an early build of Plok to be the third best platforming game behind his own Mario in first, and the rivaling Sonic the Hedgehog in second. He reportedly expressed interest in helping Software Creations make Plok of a higher quality than Sonic, even if not Mario. Ultimately, he passed up the opportunity, with Pickford believing it was due to similarities with the then-unannounced Super Mario World 2: Yoshi's Island.