From Minecraft Wiki
November 5, 2010
Alpha v1.2.1 is a version of Alpha released on November 5, 2010, to fix bugs. Although the launcher claims to have this version available, the version listed is just a duplicate of Alpha v1.2.1_01.
- Mob spawning reverted to old code.
- Leaf particle colors now reflect the biome instead of the grayscale texture.
- 4 bugs fixed
- Signs on the sides of cacti no longer crash the game
- Fixed the player getting stuck in the top of the world in SMP.
- Optimized CPU usage for mob spawning
- Music now plays in multiplayer