My recent world spawned me in an ice spike biome surrounded by other snow covered biomes. Whenever mobs (hostile or friendly) move onto a block that has a layer of snow on it, they tend to hop and rotate on the block and, in the case of mobs focused on the player, tend to lose their focus/intent on reaching the player.
Environment
Windows 7 (64 bit) with Java 7 (64 bit)
Dupe of MC-55549