Spoilers for Game of Thrones, season 7 below.
If you watched that scene in the Game of Thrones premiere and wondered why the maester refused to let Sam into the restricted section of the library, maybe it's because he remembered Tom Riddle.
That citadel maester, making his series premiere, is played by Jim Broadbent. You might remember him as Professor Slughorn in Harry Potter.
In fact, here's Broadbent talking to Tom Riddle about the restricted area of the Hogwarts library.
The situation's different—the future Lord Voldemort wanted clarification on something he had already read in an off-limits book. Sam Tarwell wanted a permission slip to go read about White Walkers. He ended up disobeying orders and sneaking into that part of the library, anyway.
So both bad boys ended up in the restricted area of the library and talking to Jim Broadwell about it. That's more than enough to send fans into a code red, "my-two-favorite-fantasies are crossing over" frenzy.
And just bravo to you if you made it through Sam's disgusting pee and poop montage and could still make the connection to Slughorn.