Spray slow cooker with non stick cooking spray. Add lid. Set heat on HIGH to preheat for 15 minutes..
Mix cake mix, water oil and eggs in bowl with mixer on medium speed for 2 minutes.
Pour batter into slow cooker. Cover with lid.
Combine pudding mix and milk. Beat until smooth.
Pour pudding over cake batter in slow cooker. Do not stir.
Sprinkle with chocolate chips.
Add a layer of paper towels over slow cooker then place lid on top. The paper towels will soak up moisture on lid and prevent it from dripping onto the cake.
Reduce heat on slow cooker to LOW and cook for 2 1/2-3 hours.
Remove paper towels.
Cake should be set around the edges and gooey throughout the center.