Preheat oven to 350 degrees F. Line 2 (12-capacity) muffin pans with cupcake papers; set aside.
In a large bowl, use a hand held electric mixer to beat together cake mix, chocolate milk, oil, and eggs on low speed for 30 seconds. Scrape sides of bowl with a rubber spatula and beat for 1 minute more on medium speed.
Use a ladle to fill each lined cupcake cup 2/3 full. Use oven mitts to place cupcakes in preheated oven and bake for 21 to 26 minutes or until a toothpick inserted in the center of the cupcake comes out clean with no wet batter.
Use oven mitts to remove from oven and let cool completely before filling and frosting, about 30 minutes.
For filling combine pudding mix, milk, and peanut butter in a bowl. Whisk for 2 minutes until smooth and thickened. Refrigerate for 30 minutes. Spoon filling into a pastry bag fitted with a medium plain tip. Fill cupcakes by inserting tip into tops of cupcakes and squeezing a couple of tablespoons of filling into each. Spread 2 tablespoons frosting on each cupcake top.
Using red gel frosting, draw squiggly lines on the frosted cupcakes so that they look like veins. Place a plastic eyeball in the center of each cupcake.