Prepare cupcakes - In a mixing bowl, combine cake mix, eggs, water, and oil.. Beat with a hand mixer or the standing mixer for 2-3 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 cupcakes to cool completely.
If the cupcakes have domed tops, use a serrated knife to trim off the dome and form a flat top. Frost with 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 eyeballs at the base of the pretzels and just above the vanilla wafer cookie.
Pipe a dot of frosting to glue on an M&M nose.
Pipe a mouth below the nose.
Notes
A flat top on the cupcakes is helpful to hold the decorations on one plane - otherwise, they start slipping or look funny at different angles.
If you use grocery store frosted cupcakes, I’d recommend taking an offset spatula/knife and just smooth out the frosting into a flat top.
Make different faces/smiles/expressions with the frosting for variety.
White candy melts can be substituted for the Nilla wafers and regular mini pretzels can be swapped for the chocolate covered variety.
You can keep these cupcakes in an airtight container on the countertop or in the refrigerator for up to a week. Feel free to freeze the cupcakes so you can have those ready ahead of time, but I don't recommend freezing them after decorating. Take note that the vanilla cookie may get soggy or soft after setting out for more than a half day or so. If you need to prepare cupcakes in advance, I would bake and frost a day ahead and then quickly pop on the decorations just before serving.