Later, during the post-credits scene, this joke is brought back up, only this time Olaf isn’t talking to the Northuldra clan. Instead, he’s explaining how some of Elsa’s other creations came to life to some of her other actual creations. This is where the Frozen tie-in is really worked into the movie, although it’s worth pointing out the entire plot of Frozen II builds on things we have learned about Elsa and Anna, their parents, and the kingdom of Arendelle during Frozen. So, I’m certainly not trying to argue the bit after the end credits is the only time the movie strives to do this. It is a fun Easter egg for fans, however. And we know how fond Disney movies are of Easter eggs.
Article source: https://www.cinemablend.com/news/2485377/frozen-ii-has-a-post-credits-scene-with-a-callback-to-the-first-movie