Okay, so they're not exactly German -- ground cherries (Physalis peruviana, or Kapstachelbeere in German) are a tropical fruit, but they are quite popular here. They are a small sweet, slightly tart fruit, and a member of the nightshade family, like tomatoes. They grow inside a papery hull, like tomatillos (Physalis philadelphica). They often appear as garnishes on restaurant plates or buffets. I finally bought some at the grocery store yesterday, and we are enjoying them at home.