The True Mance Rayder
Okay, so this gets complicated. Mance Rayder dies in the TV show when he is shot by an arrow to put him out of his misery as he’s burnt at the stake. In the books, this isn’t actually Rayder, but rather his lieutenant Rattleshirt who is under a magical disguise thanks to Melisandre. Rayder is then disguised as Rattleshirt, and even trains with Jon Snow without Snow realizing the switcheroo. Later, Melisandre suggests that “Rattleshirt” (who is Rayder in disguise) should travel to Winterfell to save “Arya Stark” (who is actually Jeyne Poole) from being married against her will to Ramsay Bolton (who is actually a turd). Rayder reveals his true identity, and says that he’ll do anything Snow wants because Snow has Rayder’s son – but Rayder doesn’t know that Snow has switched his son with Gilly’s son instead. Is all that clear? It’s no wonder this was exercised from the TV show.