I used to have a book by Nigel Rees called “Eavesdroppings”. It was full of snippets of snatched bits of conversations that people heard on buses or in the street as people passed etc. and really appealed to my daft sense of humour.
I’ve just Googled an example (not from his book).
Overheard a couple on the street: "It just fucking hurts when you bite my dick!"
What’s the best thing you’ve overheard or wish you knew the backstory to?