In a medium bowl, whisk together pudding mix and milk for 2 minutes. Let stand for another 2 minutes, or until soft-set. Pour into a greased 6-quart slow cooker.
Prepare cake mix according to package directions, adding in the 1/2 cup peanut butter.
Pour cake batter over pudding.
Cover and cook on LOW for 3 to 3 1/2 hours.
Sprinkle peanut butter chips and chocolate chips on top. Cover crock pot, but turn it off, and let stand 15 minutes to partially melt the chips.
Serve warm with whipped cream and banana slices.
Notes
Store leftovers in refrigerator. They can be eaten cold or reheated in the microwave.