She's middle-aged, gray-haired and stays up all night. Still, Heidi the cross-eyed opossum is Germany's biggest media sensation, and she has not even made her debut at the Leipzig Zoo.

Yet Heidi appears to be the next in a line of animal celebrities in Germany. The 2-1/2-year-old opossum has a growing Facebook following pushing 80,000 fans, sparked a popular song on YouTube and will soon star as a plush toy.