Heidi's poor vision – thanks to her bulging eyes – has struck a chord with the public, but zookeepers say it does not cause many problems. As opossums are nocturnal they rely heavily on their sense of smell to find their way around. She experiences no discomfort and has no problem interacting with other opossums.
Why is Heidi the cross-eyed opossum is so popular?
Peter Walschburger, a biological psychologist at the Free University of Berlin, has analysed the unprecedented attention the opossum has attracted.
He said: "It triggers a reaction in our unconsciousness when we see these creatures that make us think of children."
Link (Photo: Sebastian Willnow/AP)