Spacebunnies are planet-sized pests of the universe that burrow into spacetime tunnels, leaving catastrophic black holes behind. Seeing a spacebunny in the sky is the worst omen someone can ever hope to see, both because their presence foreshadows an inevitable slide of the planet into the black hole's gravitational pull and also because the sight of a space bunny in the sky causes all who see it to go completely and irrevocably insane, which has razed entire civilizations long before their planet was eventually destroyed.