“Thing you’d be most surprised a friend had not seen or read?”
Honestly, almost nothing surprises me anymore, and I now try to at least not act surprised about anyone’s lack of exposure to any given property, as I’m aware doing so smacks of “geek cred” judgement (which is a shitty thing, to be sure).
But sure, within the scope of this hobby, meeting someone who’s never had any experience with some version of D&D would seem unusual, since that’s usually the default entry vector.
And I will admit that I find it weird sometimes to meet someone in the hobby of a certain age who’s never heard of The Forge. I mean, the sheer amount of complaining about it in mainstream RPG fora would make me think that most folks my age would have at least heard the term.