Prepare the cookies according to package directions. Remove from the oven and transfer the cookies to a cooling rack to slightly cool.
Unwrap the peanut butter cups and then gently press in the center of the cookies. Let harden.
In a microwave-safe bowl, add the chocolate chips, and about a half-teaspoon of vegetable oil or shortening (if desired; makes it a little easier to work with!)
Microwave in bursts of 15 seconds stirring in between each burst for 10 seconds until the chocolate is melted and smooth. Transfer the melted chocolate to a plastic bag and cut off the very tip of the bag.
Pipe "spider legs" onto the cookie starting from the Reese's cup going outwards.
If desired, pipe a little melted chocolate on the back of the edible eye candies and press into the Reese's cup.