Step 1: In a large mixing bowl, combine the softened cream cheese, shredded sharp cheddar cheese, mayonnaise, garlic powder, onion powder, black pepper, and finely chopped fresh chives. Mix until all ingredients are thoroughly combined and smooth.
Step 2: On a serving platter or a piece of parchment paper, use your hands to mold the cheese mixture into the shape of a skull. Create a defined forehead, indentations for the eye sockets, and a jawline. Don't worry about perfection; a slightly rustic look can add to the spooky charm.
Step 3: Tightly wrap the shaped cheese ball in plastic wrap and refrigerate for at least 1 hour (or up to 3 days) to allow it to firm up.
Step 4: Just before serving, unwrap the cheese ball. Use black olives to create the facial features. Halve two olives for the eyes, use a small piece for the nose, and thinly slice several olives to form teeth along the jawline.
Step 5: Arrange your Skellington Cheese Ball on a platter surrounded by an assortment of crackers, pretzel sticks (for 'bones'), and fresh vegetable sticks. Serve immediately and enjoy your frightfully delicious appetizer!