Prepare a 9x13 baking pan by spraying it with nonstick spray and adding parchment paper to the bottom for easy removal.
In a large pot, melt the butter over medium-low heat. Once the butter is almost completely melted, add the marshmallows.
Stir to coat the marshmallows fully in the butter. Cook for 5 to 8 minutes, stirring intermittently until the marshmallows melt completely. Don't overcook, as this will cause the mixture to burn and the marshmallows to harden.
Remove the pot from the heat. Stir in vanilla extract and salt.
Pour in the cereal. Stir to fully combine, making sure to scrape any additional marshmallows from the bottom of the pot.
Dump out the cereal and marshmallow mixture into the 9x13 baking pan. Using a greased spoon, spread out evenly from edge to edge.
Allow the rice krispie treats to cool and slightly harden for about 15 minutes before slicing into 15 even-sized rectangles.
Remove them from the baking pan and use your hands to mold them into evenly shaped rectangles.
In a small bowl, add white chocolate chips and coconut oil. Melt in 30 second intervals in the microwave until completely smooth.
In a separate bowl, add the red sugar.
Working with only 1 at a time, dip the top third of a rice krispie treat in the melted chocolate. Then, dip the top part of the white chocolate in the red sugar to create santa's hat.
There should be a remaining thin line of white chocolate below the red sugar in order to add the coconut, but if not, use a spoon to add a small strip of chocolate before using your fingers to carefully stick in the coconut flakes just below the sugar.
Using a spoon, add another small strip of white chocolate to the bottom quarter of the krispie treat. Using your fingers, stick additional coconut to the bottom white chocolate to create santa's beard.
Place a very small amount of white chocolate on the back of 2 candy eyes and stick them in the middle of the treat. Add a small amount of white chocolate to a red candy and place this for his nose just below the eyes. (If using a candy like m&m's with a noticeable logo, flip them upside down so only the plain side is showing.)
Repeat with the rest of the treats until they're all fully decorated, or decorate half as santa and the rest like reindeer! Allow all the chocolate to harden before moving, stacking, or serving.