Breaking the bed that a villager is sleeping in causes the half of the bed that you broke to break, leaving half a bed with a villager lying on it. When breaking the other half, the villager will stay floating in its sleeping animation.

Issues during the lag: 

Whilst the villager stays floating, all mobs in the world will freeze, whilst all two high/long blocks that you break whilst this lag occurs will leave the other half there.

Another issue that occurs is that you will not be able to open chests, hoppers, ender chests, trapped chests, blast furnaces, furnaces, smokers, droppers, smithing tables and any other interactive blocks.