Spray an 8 x 8 baking pan with nonstick spray and set aside.
Place the marshmallows and butter in a large microwave-safe bowl and heat on medium power until melted. Stir together thoroughly. Pour in the cereal and stir to coat completely.
Scrape the mixture into the prepared baking pan and press until reasonably flat. This may be easier after a minute or two, but it’s a sticky procedure. You can spray a spatula or your hands with cooking spray if you like.
While still sticky, press the candy eyeballs into the top of the bars wherever you like.
Heat chocolate chips until just melted in a small bowl in the microwave. Stir in coconut oil. Use a spoon to drizzle chocolate mixture over bars. Let cool until solid. You can do this in the freezer for about 15 minutes if you like. Cut into squares and serve.