Inspired by the Deadlight quick look at the moment and the moment a character refers to the protagonist as "Mr Wayne", and Vinny whispers "...its Batman...!" and Brad agrees that it would be awesome if it is.
Has there ever been a game that had some IP license or recognisable figure in it and just totally kept it secret until it was revealed as part of a plot twist? Obviously it doesn't really make much economic sense, but it would be an awesome narrative twist.
I can't really think of an example of it happening. Burt Reynolds making a surprise appearing in Saint Row 3 playing himself was pretty great.