Place your large round pastry tip in your pastry bag and fill it with the red buttercream. Pipe a swirl on the cupcakes. Place your star pastry tip in your pastry bag and fill it with the white buttercream. Hold the pastry tip against the bottom of the red buttercream and lightly pipe a small star of buttercream. Keep doing it all around the cupcake. Make one star on the top of his hat.