Peel the hard-boiled eggs and slice them in half lengthwise. Gently remove the yolks and place them in a small mixing bowl. Set the egg whites aside.
Finely chop the green onion and celery, then add them to the bowl with the egg yolks.
Add the mayonnaise, Dijon mustard, salt, and pepper to the bowl. Mix everything together until smooth and creamy.
Transfer the yolk mixture into a quart-sized storage bag. Remove any excess air, seal the bag, and snip a small corner off for piping.
Pipe the yolk mixture into each egg white half, filling them evenly.
Lightly sprinkle paprika over the eggs for a festive touch.
Slice the cucumber lengthwise into thin strips using a mandolin or vegetable peeler. The strips should be pliable enough to fold into ribbon shapes for the Christmas tree.
Fold a cucumber strip into a ribbon shape and insert a wooden toothpick through the center. Place a pomegranate aril on the tip of the toothpick to resemble a tree topper.
Insert the bottom end of the toothpick into the center of a deviled egg. Adjust the cucumber ribbons as needed to create a tree shape. Repeat for each deviled egg.
Serve your festive Christmas Tree Deviled Eggs and enjoy!