Alien Villagers (also known as Moon Villagers) are currently the only passive mobs that can be found on the Moon. They live in the Moon Villages.
Currently they do not have any trade system. They do not breed either, although Baby Alien Villagers can be spawned on creative mode with Spawn Eggs. Killing them does not give any item or experience point. Like the vanilla Villagers, they will run for a shelter (with a wooden door) at night and during a rain, and stay indoors until the morning or clean weather.
Evolved Zombies and vanilla Zombies do not attack them. On the other hand, if the player attacks any Alien Villager, Iron Golems nearby will pursue the player (only in Survival mode).