Line a baking sheet with parchment paper and set it aside.

Melt the butter in a large pot over medium heat. Add the mini marshmallows and stir until fully melted and smooth.

Remove the pot from heat and stir in the vanilla extract.

Add the Rice Krispies cereal and mix until every piece is coated.

Let the mixture cool for two minutes until it is safe to handle but still pliable.

Scoop out portions and shape them into bone forms by rolling and pinching the ends to create the classic bone look. Place each bone on the prepared baking sheet.

Melt the white chocolate melts in a microwave-safe bowl in 20-second bursts, stirring between each.

Drizzle or pipe small lines of melted white chocolate across the bones to add skeleton details. Let the chocolate set before serving.