I never quite understood the meme of getting diarrhoea after eating fast food (chiefly, taco bell) because the couple of times I'd tried it in Australia, it seemed average but entirely uneventful food and didn't cause any sort of adverse reaction for me. Nor did KFC or any other one I can think of where that's been made as a joke. It was all just... fast food.

Then the penny, rather like an anvil, dropped when I realised it must instead be describing by proxy the food safety standards inherent in US fast food vs elsewhere around the world. I hadn't then also factored this specific issue into that broader realisation, but it definitely tracks.