Villagers float if you push them while they're sleeping.

While a villager is sleeping in a bed, if you stand on the bed, the villager can be pushed and will begin to float. While floating in this way the villager will pass through blocks. The way you're standing on the bed determines the direction in which the villager will be pushed. Thankfully, this does not seem to harm the villager. They don't take damage from suffocation, if you try to punch where they're floating nothing happens, and zombies don't notice them. When morning comes or if you sleep in the bed, the villager will exit the bed in the normal location.