Grab a big bowl and beat the softened cream cheese until it's nice and smooth. Pour in the sweetened condensed milk and vanilla, and mix it all up until it's totally combined.
Sprinkle in the instant pudding mixes and pour in the cold milk. Now, whisk or beat everything for a good 2–3 minutes—you'll see it get really thick. Let it just sit there for about 5 minutes; it'll firm up a bit more.
In a separate bowl (or just rinse out the first one!), whip the heavy cream and powdered sugar together until you get stiff peaks. Don't go too far or you'll end up with sweet butter!
Delicately blend the light whipped cream with the pudding mixture. Go slow and be gentle to keep it light and creamy. Fold it just until everything is smooth and blended.
Time to layer! In your 9x13 dish, spread just a thin base layer of the pudding. Top that with a single layer of Nilla wafers, then a layer of banana slices. Repeat these layers two more times, always finishing with a nice thick layer of pudding on top.
This next step is key: cover the dish tightly with plastic wrap, pressing the wrap directly onto the surface of the pudding. This keeps air out and prevents a weird "skin" from forming. Now, walk away! Let it chill in the fridge for at least 8 hours, but honestly, overnight is magic—the flavors melt together and the wafers get perfectly soft.
When you're ready to serve, you can whip a little extra cream for on top if you want it extra fancy. Sprinkle some crushed wafers over everything for that classic look, and dig in!