A common person from your era of expertise suddenly appears in our time via a time travel accident. What would be the strangest thing to them, and why?

I know that the more you go back, the more the answer just becomes "everything". If so, I'd love to see if there's something that'd perplex them that we wouldn't think that it would (as much).

Also, for the sake of simplicity, lets just assume that the magical time travel thing also teaches them the appropriate modern language they need.