When Benedict Cumberbatch appeared as the antagonist of Star Trek Into Darkness, the identity of the character he was playing was kept very secret, to the point that JJ Abrams straight-up lied about it. But apparently Cumberbatch spilled the beans to one special person.
Appearing on the Graham Norton Show recently, Cumberbatch revealed that, while he's generally very good at keeping spoilers to himself, he felt, in this case, that the late Stephen Hawking deserved to know. So, while in production on Into Darkness, and three margaritas deep, Cumberbatch let slip that he was actually playing Khan in the film, the famous antagonist from Star Trek II: The Wrath of Khan.
No word in this clip on how Hawking, who passed away last month after a lifelong struggle with ALS, responded to the gossip, but my best guess is: "Duh."