Warning: If you haven't seen The Originals yet, don't read this tweet. It contains spoilers. As you all know, the character of Kol Mikaelson is back in The Originals, but he is in a different body (actor Daniel Sharman is playing him). The reason why Nate couldn't come back and reprise his role as the young Mikaelson is because he wasn't available back then cause of his Supernatural: Bloodlines project (which ended not being picked up). So, the writers had to come up with something new. This doesn't mean we will never see Nate as Kol, for now he will be seen in flashbacks. And who knows, maybe one day Kol will be back in his original body. We will have to wait and see.