Cream the butter and sugars together in the bowl of a stand mixer using the paddle attachment. Add the peanut butter, egg, and vanilla. Mix well and scrape the bowl.
Combine the flour, baking soda, and salt. Add to the butter mixture all at once and mix until just incorporated.
Working in batches, scoop dough into balls and place onto silicone lined baking sheets about 2-inches apart -- up to 12 cookies per baking sheet (recipe makes 30 cookies in total). Bake at 350 degrees Fahrenheit for 10 minutes or until just set. Allow cookies to cool slightly on the tray for 2 minutes.
Lightly press one mini peanut butter cup in the center of each cookie while still warm. Allow to melt slightly. As soon as the peanut butter cups are soft enough, place two eyeballs on the side of each peanut butter cup. Repeat for all cookies on the tray then move the tray to the freezer to allow the chocolate to set.
Melt the chocolate chips and coconut oil (or shortening) in the microwave in short 10-20 second bursts until melted. Place melted chocolate inside a zip-top sandwich bag. Cut off a small piece of the corner and pipe 8 legs on each cookie in an "L" shape to create a bent leg look.
Return cookies to freezer to set the chocolate. Remove and store cookies covered with plastic wrap or in an airtight container up to 5 days.