Preheat oven to 350 degrees F. Line a muffin pan with paper liners and lightly spray with nonstick cooking spray.
Into a large bowl, sift flour and cocoa powder together. Whisk in both sugars, baking soda, baking powder, and salt until well combined. Whisk milk, oil, vanilla and both eggs into the dry ingredients just until all ingredients are evenly incorporated. The batter will be runny. Divide batter evenly among muffin pan cups, filling each about 2/3-full.
Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean. Let cupcakes rest in the pan for 5 minutes, then remove to a cooling rack to cool completely before frosting.
For Orange Frosting:
In a medium bowl, mix white frosting with food coloring until desired shade is reached. Pipe frosting on top of cupcakes. Place 1/4 cup sprinkles on a small shallow plate, turn cupcakes upside down and press gently against sprinkles to coat evenly.
For Meringue Ghost Frosting:
Simmer 1 inch of water in a medium saucepan set to medium heat.
Place egg whites, sugar, cream of tartar, and salt in the bowl of a stand mixer. Place bowl over the saucepan, making sure the bottom is not touching the water. Heat mixture for about 6 minutes, whisking constantly, until sugar dissolves and the mixture is hot to the touch (about 120 degrees F).
Transfer bowl to a stand mixer fitted with the whisk attachment. Whisk on medium speed for 1 minute. Increase speed to high and whisk until stiff, glossy peaks form, 5-10 minutes more. Add vanilla and whisk until just incorporated, about 1 minute.
Pipe frosting on top of cupcakes with a wide round tip. With a toothpick dipped in black food coloring, add eyes and a mouth to the meringue ghosts.
Serve immediately or store in an airtight container at room temperature for up to 3 days.