When you make a Villager Breader (Farm) with many Villagers the Iron Golems will spawn, but sometime - gliched in the ground. (Stucked in a farm-land block with seeds on top). The bug is in Minecraft 1.9, Minecraft 1.9.1 Pre-release 1, Minecraft 1.9.1 Pre-release 2, Minecraft 1.9.1 Pre-release 3;
The bug is not always, but i saw it in a row 4-5 times. It's buggy in Singleplayer worlds and SMP (Multiplayer) Servers (Many tests, many worlds, many versions)