Kristoff Knew Anna was Healed by Pabbie before Opinion/Headcanon
There seems to be a lot of speculation in the scene when Kristoff offers to take Anna to the trolls of whether or not he knows that Anna was the same girl he saw years before. Jennifer Lee has confirmed that Kristoff does indeed know, although she hasn’t made specifics about how MUCH he knows. Here is what I think about it:
Kristoff may not have initially known that he had seen the royal family. as a boy. But because he grew up with the trolls, he would have asked about what he saw and learned the truth. In that case, Kristoff had learned that Elsa had ice powers and Anna was healed by Pabbie before.
In Anna’s case, Kristoff may have been told that she had a white streak in her hair from being struck by Elsa. Now it’s not made clear if he notices it before Elsa strikes her again, but it is made perfectly clear when he sees the streak grow bigger and turn more of her hair white.
In facf, look in the third and fourth gifs: when she asks if it looks bad, he only hesitates because he is thinking about the last time he saw a girl with a white streak in her hair: he scrunches his eyes, trying to remember, then his eyes widen because he not only realizes that Anna was the same girl he saw, but because he knows what her fate will be if she does not get help. And he realizes that there may be one hope for her survival: the trolls.
So then after he snaps back to reality, Kristoff insists on bringing Anna to his family so they can help her. And the final confirmation for me that he knows that Anna was saved before is when he turns around after she asks, “How do you know?” and looks at her when he answers, “Because I’ve seen them do it before.”
On the side, Kristoff does have significance to the story besides the second love interest. Anna would never have made it to the North Mountain without him or received help from the trolls without him, either, even if Kristoff did not truly save her from her frozen heart curse.