Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large bowl, combine the yellow cake mix, undrained crushed pineapple, eggs, and vegetable oil. Mix until just combined.

Pour batter into the prepared baking pan and spread evenly.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool completely before adding the topping.

In a separate bowl, whip together the whipped topping and instant vanilla pudding mix until smooth and creamy.

Gently fold in the undrained crushed pineapple.

Spread the topping evenly over the cooled cake and refrigerate for at least 30 minutes before serving.