EarthBound 64 (also known as MOTHER 3 in Japan, but not to be confused with the GBA game of the same name) was a cancelled sequel to the 1994/1995 Super Famicom/SNES game MOTHER 2/EarthBound (respectively). The story follows Lucas, Claus, and Flint, a family of 3 who lost their mother/wife, Hinawa.
The game was originally to be on the 64DD add-on and have many uses of the 64DD, but not all of the uses are well known. After the 64DD turned out to be a commercial failure (thus preventing any localization of the extension), the game was going to be moved onto a standard N64 cartridge. The two big problems were that Shigesato Itoi and his crew had little to no experience with 3D titles, and without the aid of the 64DD, the game had many constraints such as time and memory. Eventually, the title was pushed back until it was finally cancelled.
The name MOTHER 3 was never forgotten, though. A few years later, after a MOTHER 1+2 commercial, it was announced that MOTHER 3 was in the works, and the final game was later released in 2006. A few changes in this version were obvious, however there are some connections between the 2 versions. Claus was no longer a protagonist, a few characters were added, but the biggest change was the 2D gameplay.
It was also rumored the story was to be darker on the Nintendo 64 version. Unfortunately, the rest of the world was left in the dust and never received any EarthBound 2, however unoffical translations are available.