My friend forgot their umbrella at the office.
They nervously answered the phone.
They’re a lazy motherfucker.
I gave my friend a hug and wished them a speedy recovery.
Any of those sound unusual, or like they’re referring to more than one person?
For the US, I’d say a pretty strong contender is Woodstock, NY, with a population of around 6,000, and of course famous for the music festival of the same name (even though the actual festival was something like 60 miles away in Bethel)