1. Slice eggs in half lengthwise, and carefully remove yolks, keeping egg whites intact.
2. Grate egg yolks using small holes of a box grater. Mash together yolks, mayonnaise, and next 3 ingredients. Add hot sauce, if desired. Stir spinach, onion, and poppy-seed dressing into yolk mixture.
3. Spoon or pipe yolk mixture into egg white halves. Top with bacon.