First Germany lost Knut, now it has lost Heidi. The opossum became famous last December when she went on display at the Leipzig Zoo because of her crossed eyes. The eyes were the result of her being overweight, zookeepers said. She also suffered from arthritis, which led zookeepers to put her to sleep on Wednesday. She was three-and-a-half years old, apparently “old age” for an opossum.