Villager Farmers Replaced with Clerics

I loaded a default superflat world, and walked into a village. Where I would have expected brown-robed villagers there were instead a surplus of purple-robed cleric villagers.

What I expected to happen was...:
Brown-robed villagers in the village.

What actually happened was...:
Purple-robed villagers where brown-robed villagers should be.

Steps to Reproduce:
1. Load a superflat world.
2. Find a village.