Writing scripts backwards is a technique that works well for comedies.
Having a final scene so proposterous as to be hilarious can be a starting point in which every previous scene can lead to a justification of the unliklyhood. So I have been making a list of final impossible scenes like Chuck Schumer being handcuffed to Ted Cruz or Trump stuck in an elevator with Himmler's ghost. The list doesn't look like ideas for a suspension of belief but more like a supension of sanity. I welcome another POV.