I also play a Star Wars character, but one of the lesser known ones. I totally don't mind someone knowing about the universe and commenting about the Empire and Jedi and the Well-Known Characters (though I'd be mindful of players of said characters if they were in my game), but I draw the line at "your character has not read the total of two novels this character shows up in, sorry". It feels fair to me and lets people have some fun about the idea of fourthwalling in general.

And I'm in agreement with you about historical figure characters. Yes, you know about Catharine di Medici, but you don't know the specifics of her storyline in Reign or The Serpent Queen or the 1956 film about Diane de Poitiers.