The Squared Schrödinger Box allegory: you cannot know if the first cat is alive until you hear it mourn the second cat, which happens only if it decided to open the smaller box; neither can you know if the second cat is alive unless it manages to get out of his own bow and mourns the first cat's death. To see which cat survived, or if any survived at all, you need to open the first box, or both; until then, both cats are half-alive, so there's only one live cat in the bigger box.