Preheat the oven according to the cake mix package directions. Grease a 9 x 13-inch baking pan.
Prepare the cake batter according to the package instructions and pour it into the prepared pan
Bake until the center is set and a toothpick inserted into the middle comes out clean or with a few moist crumbs.
Remove the cake from the oven and let it cool for 10 to 15 minutes.
Use the handle of a wooden spoon or a large straw to poke evenly spaced holes throughout the cake.
Whisk the instant banana pudding mix with cold milk until smooth and thickened.
Pour the pudding over the cake, spreading it evenly and gently pressing it into the holes.
Cover and refrigerate for at least 1 to 2 hours.
Spread the whipped topping evenly over the chilled cake.
Arrange the sliced bananas and strawberries over the whipped topping.
Drizzle with chocolate fudge sauce and sprinkle with chopped walnuts or pecans.
Add rainbow sprinkles and maraschino cherries, if desired.
Chill for another 30 minutes before slicing and serving.