Earthbound 64 or, as it was known in Japan, Mother 3, never saw the light of day. But new footage showing the game in action gives us a hint at what might have been.
The video below is footage taken at SpaceWorld 1996, Nintendo's Japanese showcase event, and was unearthed by YouTube channel kukun kun (thanks, ResetEra). At the 10:27 mark we see footage of Mother 3.
The game doesn't look up to much by today's standards, of course, but it was a hugely anticipated title for Nintendo 64 fans and, unfortunately, perhaps too ambitious for Nintendo's console (that interior scene in particular looks like it would have given the N64 trouble). Eventually, the game was cancelled in 2000 as Nintendo turned its attention to the GameCube.
Mother 3 was reannounced for the Game Boy Advance in 2003 and launched in 2006 in Japan. It never came out on these shores.
Interestingly, right after the Mother 3 footage we see early gameplay of a pre-launch version of Nintendo classic The Legend of Zelda: Ocarina of Time.