Preheat oven to 350 degrees Fahrenheit. Spray with cooking spray in three 9 by 13-inch baking pans.
Combine cake mix, butter, eggs, orange juice, and vanilla in a stand mixer or with an electric mixer on medium speed for three minutes, scraping the sides as necessary.
Fold oranges in.
Pour batter evenly into each of the three prepared pans.
In the preheated oven, Bake for 16 to 20 minutes, or until golden brown and a toothpick inserted into the center comes out clean.
On a cooling rack, allow cakes to cool fully before transferring them to the refrigerator until ready to frost.
For Frosting:
After the cakes have cooled, mix whipped cream, crushed pineapple, and pudding mix in a bowl.
Apply one-third of the frosting to the first cake layer.
Repeat with another layer of frosting and the second piece of cake.
Add the final cake layer, followed by the remaining frosting.
Before serving, the cake should be stored in the refrigerator for at least three hours.
If desired, garnish with more mandarin orange slices.
Notes
Ensure that the cakes have cooled completely prior to frosting.
Cool Whip in a frosting may melt if exposed to excessive heat.
This also indicates that the cake should be served and stored cool.
For additional taste and texture, you can add coconut shreds to the frosting.