Another funny one I ran into a few times was how for a time like 8:30, we'd say "half eight" in the UK, but when I would casually say this in the US people would be like "half eight? you mean four?" It had never occurred to me this common British parlance would be unintelligible elsewhere. Of course, there are just as many things the other way around, although watching a lot of US TV will take care of that.
In dutch, half eight is 7:30 too.
7:40 is weird: "ten over half eight"
That said, the way the French count numbers is, I think, universally confusing. Knowing the French, this is intentional :P
So for instance if I might say “These three things,” he would say “these tree things.”
He was clearly able to make the sounds but in some cases he couldn’t. I never felt comfortable asking about it because I thought it might be a class thing.
The other one is asking for a cheese sandwich - that seems to throw Americans every time.