Invisible crab aliens were raining from the sky. We (some people) couldn't see them, only feel their prickly crustacean feet on our skin as they ran over us. We all climbed up into the attic of a house to hide with some other refugees. We stayed there several months. Eventually, we came down and learned that the crabs had combined into larger multi-crab alien people who were not hostile, they were just sort of weird. Each had a totally different shape-- squat, tall, different numbers of limbs, spherical, elongated, etc. They were now integrating into human society-- still invisible, so they wore robes so humans knew where they were.