Heat your oven to 350°F (175°C).
Prepare the penne pasta according to the package directions until just tender, then drain well.
In a large bowl, blend together the softened cream cheese, ranch dressing, and shredded cheddar cheese until silky smooth.
Stir in the shredded chicken, bacon bits, and chopped green onions, seasoning with salt and pepper as you like.
Carefully fold the cooked penne into the mixture, ensuring every piece is coated.
Spread the pasta mixture evenly into a greased 9x13-inch baking pan and top with the shredded mozzarella.
Bake for 20 to 25 minutes until the cheese on top bubbles and takes on a golden hue.
Allow the casserole to cool briefly before serving, and sprinkle extra green onions over the dish if you like.