In some circumstances, a villager will not have most of his clothes, or at least it will seem like he doesn't.

How did this happen?

I was flying around in my creative world, and there was a big glass cube that I made.

There was a villager running around. I looked at him, and he was half naked. When I came closer, he had all his clothes on him.

Steps to Reproduce:
1. Put a painted glass between you and villager, no matter how close or far.
2. Step away from the villager for at least 16 blocks.
3. Look at the villager through painted glass.