1Spray 4 1/2-quart slow cooker with baking spray with flour.
2In large bowl, beat cake mix, water, melted butter, eggs, vanilla and pudding mix with electric mixer on medium speed until smooth. Pour batter into slow cooker.
3Fold frosting into batter in slow cooker with spoon, leaving ribbons of frosting running through batter.
4Cover; cook on High heat setting 2 to 3 hours or until cake is set in center. To serve, spoon hot cake from slow cooker, and top with scoops of ice cream.