After the troll heals young Anna, he spends some time delicately explaining that he’s now going to remove Anna’s memory of her sister’s powers, but replace those memories with fake memories that are just as fun, so that she’ll still remember he sister fondly. Here’s more from that Scriptnotes interview with writer Jennifer Lee:
- John August: So, one of the biggest narrative asks you make of the audience is that these memories are taken out, and so Anna remembers the joy she used to have with her sister but not that her sister has powers....
- Jennifer Lee: I think every now and then we have to make these decisions where just have to do what you have to do. … I was frustrated about dealing with the fact that I wanted to Anna to… — If the girls can’t remember, if Anna can’t remember the joy they had together, then there’s no reason to root for the relationship because it doesn’t mean anything. But, we have to — if she remembers that her sister has powers people felt that she seemed selfish anytime she did anything for herself or stood up to her sister later… it was the best thing just to get us through, was sometimes you just have to do what you have to do but just make a real point of it and the audience will go with it.
- Aline Brosh-McKenna: Just do it. And also what I think people do is sometimes when they reach a narrative thing where there is a big buy they add a lot of corollary details. You just state it. That’s the way it is. She can remember this and not that. Let’s keep going.
- Jennifer: And let’s keep going. And that was the best advice just because even if it wasn’t — and I’m never going to think it’s perfect because I’m always going to personally bump on it — everything else went where it needed to go.
- Aline: Works completely.
- John: It was a necessary thing to do. And I think you couldn’t have done three of those in a row. We would have lost faith in you and the movie, but you got one and you used it really, really well.
- Jennifer: That’s what they said. “Here’s your wild card. Go. We’ll buy it.”
To fill the empathy hole, they had to dig a motivation hole, and then they filled the motivation hole by digging a plot hole, and then they had to leave it there. It’s an odd and awkward bump in the plot, but it was necessary to maintain the character’s empathy and motivation, so it was totally worth it.