And let's not even get into whether the water molecule is the same two Hs and O that it was when it was in Hitler's mouth. Or, holy hell, what if his water became your muscles! Which, you know, is another possibility.

This assumes that all the water on the planet has been evenly mixed in about 80 years since Hitler's death. I'd say if you're living in New Zealand you're likely a lot safer than if you have lived 80 years near germany. I assume the issue is less "Hitler rain" than Hitler ground water.

But molecularly, not just by the liter, the air you breathe is guaranteed to contain a molecule of Caesar’s last breath from when he was stabbed with every breath we take. There’s way more air than water, so it stands to reason that not only are you drinking water that Hitler has drunk, you’re drinking Hitler’s pee! And Alex Trebek’s pee, I suppose.

So it’s probably not been in Hitlers mouth. Dinosaur piss I’ll leave as an exercise for the reader.

I'm on it. Dinosaurs lived for millions of years, so if we assume at least one dinosaur per year, there were likely at least a million dinosaurs. Dinosaurs are also very big. This means they probably stored a lot of pee. How much pee? Based on their size, probably at least a gallon or more. So now you've got 1 million gallons of dinosaur pee. With 8.025 billion people on Earth, that's roughly 1/2 teaspoon of dinosaur pee for every living human!