1. Preheat oven to 350° F.
2. In a large mixing bowl, combine the cake mix, pumpkin puree, water, oil, eggs, pumpkin pie spice, and vanilla. Mix with a hand mixer for about 2 minutes or until smooth.
3. Pour mixture into a greased 9x13 inch pan; bake for 25-30 minutes or until a toothpick inserted in the center comes out clean. Set aside to cool for 15 minutes.
4. Once cooled, poke holes in the cake using a wooden dowel or the end of a wooden spoon. Pour the sweetened condensed milk into the holes; cover and refrigerate 2 hours.
5. Remove from refrigerator and spread cool whip evenly over the cake. Top with pecans, caramel syrup, or any toppings you desire. Store covered in the refrigerator.