Spray 4-quart CROCK-POT slow cooker with nonstick cooking spray. Add pudding mix; whisk in milk.
Prepare cake mix according to package directions. Carefully pour cake mix into CROCK-POT slow cooker. Do not stir.
Cover; cook on HIGH 1½ hours or until cake is set.
Serve warm with whipped topping, if desired.
Garnish with candies.