minecraft
Not to be confused with Classic 0.27 SURVIVAL TEST.

Classic 0.28 refers to two internal development versions made by Notch made during Survival Test. They are versioned under "0.27", but are indeed early versions of 0.28.

Sheep (October 25, 2009)

Crying Obsidian Programmer Art
This section documents an unreleased version. 
While there is proof of this version's existence, it was never released to the public.

Word of Notch post

Bleached Sheep (October 25, 2009)

Crying Obsidian Programmer Art
This section documents an unreleased version. 
While there is proof of this version's existence, it was never released to the public.

Word of Notch post; Youtube Video

Creative (October 26, 2009)

Crying Obsidian Programmer Art
This section documents an unreleased version. 
While there is proof of this version's existence, it was never released to the public.

Word of Notch post