Separate your frosting evenly between three bowls.
Use food gel coloring to tint one green, one orange and one purple, adding food coloring until you reach the shade you want.
Spoon the frosting into three separate piping bags with a Wilton tip 233 on the end.
Pipe the frosting onto the top of your brownies, releasing as you pull the bag up and away to create the "hair."
Continue adding frosting until the entire top of the brownie is covered.
To finish off the brownies, add royal icing eyes, bone shaped sprinkles and colored pieces of fondant or candies.
Working ahead: If you want to save some time by making your brownies in advance, they can be kept for 3-4 days at room temperature in an air tight container or plastic wrap.
Store bough frosting: I recommend a fluffy frosting over a creamy frosting as the fluffy kind makes for a "hairier" look. A creamy, stiffer frosting is more likely to simply stand straight up.
Food coloring: Be sure to use a gel food coloring when tinting your frosting as a liquid food coloring will change the consistency of the frosting. If you're going for a really pigmented color, the liquid food coloring will make the frosting too runny.
Fill that piping bag like a pro: Spoon your frosting onto a large piece of plastic wrap, roll and twist the ends. Trim one end so there’s about ½” in length, drop your frosting into the piping bag (short end first) with the tip already on and pipe!
Piping with just one tip: If you're working with just one 233 tip, I recommend piping just one color at a time and using piping couplers to make it easy to remove the tip. Be sure to rinse out the tip between each color.
Storing frosted brownies: While the finished brownies don't store well because you can't cover the frosting without ruining the design, you can place them in an air tight container that can be closed without touching the frosting. These brownies will keep for 3-4 days from the day they were baked.