BS Zelda no Densetsu: Inishie no Sekiban (often wrongly cited as "Kodai no Sekiban") is a Japan-only Satellaview game which was playable three times in the Satellaview's lifespan for four hours per playthrough...which is sad, because it's actually pretty awesome.

It's effectively an episodic quest in the Hyrule of A Link to the Past, taking place six years after that game (and concurrently with Link's Awakening) with new dungeon layouts, some time-specific sidequests, a five-digit rupee counter, and several other unique elements and characters. The game wasn't playable outside the live broadcasts, and Nintendo hasn't really mentioned it or its Satellaview brethren since (they're briefly noted in Hyrule Historia, and even then they're not considered part of the official series timeline; a fan-made extension of said timeline, which includes this game and various other licensed media, is here), although the rental shop idea was later used in A Link Between Worlds - which also takes place in the Hyrule of ALTTP.

Mind you, gamers (especially English-speaking ones) aren't out of luck: The BS Zelda Homepage has spent quite a few years restoring and translating the ROMs (as The Legend of Zelda: Ancient Stone Tablets) for this exact purpose, with the stipulation that the ROMs will be removed if Nintendo files a request (or, presumably, internationally releases them through Virtual Console or a Zelda compilation). The project was completed in October 2016 when the only element yet to be restored, a streaming English version of the radio program that played alongside the live broadcasts, was added as MSU-1 patches.

Unused Items

After collecting everything in the game, two item slots remain empty. The Magic Cape and Book of Mudora, while coded into the game and fill these slots when hacked into the player's inventory, cannot be obtained normally.

The Magic Cape works as usual (you become invisible and invincible at the cost of magic power), but the Book of Mudora does nothing; as it fills the last slot in the A-button portion of the status screen, you were likely supposed to find the Book and either use it yourself (as in ALTTP) or give it to Zelda.

The BS Zelda Homepage's Ancient Stone Tablets: Master Quest hack adds them as hidden items, with the latter required to get the Master Sword.

ALTTP Overworld Remnants

If you go into Episode 1, 2, or 3 with a complete inventory (using a hacked save or Episode 4 save file), you can explore the overworld past the normal week boundaries. Problem is, the areas were only really changed from ALTTP as they were needed, resulting in a glitched overworld somewhere between ALTTP and Sekiban.

The sprites outside of the boundaries use the wrong tilesets, so they appear as glitched enemies. All Dark World warps are missing, while trying to use a water warp will crash the game and entering a cave or other indoor location will likewise cause strange glitches. Some don't allow you to enter the cave at all.

Unused SPC Music

Although the ALTTP SPC music is in this game's code, only the "Dungeon Clear" track is actually used in-game. The other ALTTP songs were instead streamed from the Satellite Radio Soundlink linearly. While that full soundtrack is available, current popular ROM hacks (such as those by the aforementioned BS Zelda Homepage) add code to use the ALTTP SPC music.

Unused Sprites

Both the Satellaview Male and Female player characters have two unused sets of sprites in the ROM data. One is equivalent to the scene in ALTTP where Link prays to open the Desert Palace, while the other has them being transformed into a rabbit.