In a large mixing bowl, combine the cake mix, eggs, water, and oil. Beat with a hand mixer or stand mixer for 2 to 3 minutes until fluffy and well combined.
Line a muffin tin with cupcake liners and fill each liner ⅔ of the way full. Bake according to the cake mix package instructions (approximately 15 minutes at 350°F).
Allow the cupcakes to cool completely on a wire cooling rack.
If the top of the cupcake has a domed top, use a serrated knife to trim off the dome and form a flat top. Frost cupcakes with the chocolate frosting.
Transfer about ½ cup of the frosting to a small Ziploc bag and cut a very small opening in the corner to use it as a piping bag.
Place one vanilla wafer along the edge of each cupcake (off-center).
Place two miniature chocolate-covered pretzels above the vanilla wafer to form the reindeer antlers.
Use the “piping bag” to pipe two small dots of frosting and place two candy eyes at the base of the pretzels and just above the vanilla wafers.
Pipe a bit of frosting to glue on the M&M nose.
Pipe a mouth below the nose.