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.
Add chocolate chips to a plastic zip-top bag. Melt in 30 second intervals in the microwave until smooth. Snip a small corner off the bag. Use the melted chocolate as the glue to hold on the other decorations.
Place a small dot of melted chocolate in the upper center of the rice krispie treats and quickly press the red candy into the chocolate until it sticks. (If using a candy like m&m's with a noticeable logo, flip them upside down so only the plain side is showing.)
Now, add 2 chocolate dots for the eyes right above the red candy. Press the candy eyes into the chocolate until they stick.
Cut or break the pretzels in half to create antlers. You may need more than 15 pretzels, in case any break while cutting.
Again, use the melted chocolate to add 2 small lines on top of each rice krispie treat. Stick the halved pretzels into each line.
Allow all the chocolate to harden before moving, stacking, or serving.