Sipke Ernst. This game is in Wonderboy by Simen Agdestein.
Magnus Carlsen-Mate In 12

Difficult to say. Just looked like a natural move. The most important thing is that if black captures it, it allows Qxe6+ which is obviously interesting. That's pretty much enough to play it in a fast game. It is also easy to see that it happens to get the piece back again after Qxe6, although Carlsen found a better continuation, and no more is needed to see the move is good.. Other reasons why Ng6 should be considered a candidate move in this position are that it is near the opponent's king (hence has more potential to have a useful effect) and that it threatens a rook (which makes it a tempo move, which limits black's replies). That it is a chess problem makes it easier to guess, as it looks like exactly the sort of move that tactical problems often start with (a sacrifice against the opponent's king).
The first move is a surprise, and the next
11 are quite unique as well.
Bonus: Can you name Carlsen's opponent
in this game?