GoldS has found an unused icon in Kirby’s Dream Course: “This icon was probably supposed to be used for the Mix “ability” in the game, which gives you a random ability from an ability roulette. The icon is never used in the game. There IS a Mix enemy in the 2P mode, but this graphic is never displayed. It looks almost identical to the Mix icon from Kirby’s Adventure, apart from a different palette.” In the japanese game code you can even find 11 unused levels (check the video), that were removed completely from the USA rom. Big props to GoldS for this find!
An interesting note: in the beginning, the game was not going to be a Kirby title. Rather, it was intended to be a miniature golf game entitled Special Tee Shot. It was only midway through development that the developers retooled it with elements from the Kirby series. Special Tee Shot was eventually released in Japan only on the Satellaview add-on. [Info from Wikipedia]
You can find more about the Kirby series in the WiKirby!