Arwing
The Arwing is the title of the spacecraft flown by Fox McCloud in the Nintendo StarFox series. The ship has many different models such as the Arwing II. The Arwing's relevance to Zelda is as a hidden enemy, which can be unlocked via moving around data somehow. Once found, the Arwing attacks similarly to other flying enemies. However, the Arwing can fire its laser weapons from the StarFox games.
The reasons for the Arwing being in the game, under the surface, is unknown. Its likely the designers placed it in the game as an April Fool's style joke as a surprise from Nintendo executives playing the game or quality checks. Its also not known why the Arwing wasn’t removed before release, and it certainly possible to find within the games code in cartridge form as well as its Nintendo GameCube and Virtual Console counterparts. Another possibility is they were early enemies designed to show off or test the z-targeting system. On consoles, this feature can be accessed with a Gameshark or an Action Replay. However, this can easily damage the game or the system.