1 package white cake mix prepared as according to directions.
Cook cake. In a bowl combine and spread over cake.
1 can mandarin oranges undrained
8 ounces Cool Whip
1 can crushed pineapple undrained
1 package instant vanilla pudding mix- prepared as directed on box.
I would do this a tad different- I would pour the fruit and juices over the cake, then spread pudding on top of the cake then top with cool whip. Just my personal preference.