Wash cucumbers, cut in half lengthwise, seed, and dry with paper towel; chill. Clean and stem mushrooms. Clean and hollow out cherry tomatoes, invert and chill. Cut potatoes into tiny cubes.
In large bowl, combine potatoes, celery, onion, green pepper and egg. In a small bowl, mix together mayonnaise, vinegar and sugar. Add to potato mixture. Add salt and pepper to taste. Chill. Stuff cucumber halves, mushrooms and cherry tomatoes with potato mixture. Cover and chill until ready to serve. Slice cucumbers into 1" pieces. Sprinkle with crumbled bacon. Arrange on lettuce-lined platter with tomatoes and mushrooms. Sprinkle all with paprika. Makes 6 dozen appetizers.