Wash and core the apples. Slice them into ½-inch thick rounds. Use a small bone-shaped or circular cutter to make “skull bites” from each slice. Brush each slice with lemon juice to prevent browning.
In a microwave-safe bowl, combine 1 cup of caramel sauce with 1 tablespoon of milk (optional). Microwave in 20-second intervals, stirring each time, until smooth.
Pour some of the melted caramel into the skull-shaped silicone mold and allow to set (chill briefly if needed). Alternatively, dip apple slices halfway into the caramel and place them on parchment paper to cool.
Melt white chocolate chips in the microwave and stir until smooth. Place pretzels, marshmallows, chocolate candies, and nuts in small bowls. Arrange cheddar cheese and turkey slices in groups.
On a large serving tray, arrange the apple slices and caramel skull bites in the center. Place cheddar and turkey slices around the edges. Fill in gaps with pretzels, grapes, marshmallows, candies, and other toppings.
Drizzle extra caramel over apple slices. Scatter white chocolate chips and gummy worms around for color. Add small skull candies or cookies to make the display more festive.
Serve immediately or refrigerate for up to 1 hour. For best results, add drizzles and toppings just before serving to avoid sogginess.