in the opening flashback, anna and elsa are playing with small snow figurines. the two young princesses have an array of little snow people and creatures, and there were some disney characters among them. one of the figures is baymax, the lovable robot from disney's 2014 animated movie "big hero six."
when anna and elsa hear the story of the enchanted forest for the first time, there's a small horse figurine sitting on elsa's bedside table. later in the movie, it's revealed that the water spirit is a mythical horse (called the nokk). elsa tames it and rides it to ahtohallan.
anna is more focused on elsa than kristoff for the first part of the movie, and this was reflected in the couples' costumes. but once the cloak is gone, anna's outfit actually matches the one kristoff has been wearing the whole time.
there's a hidden mickey somewhere in the scene when olaf sings "when i am older." "there's one mickey mouse hidden in there," the head of animation of "frozen 2," becky bresee, told insider. "you have to find it though."
you might have noticed that a scene shown in the trailer for "frozen 2" never appeared in the movie. the very first teaser for "frozen 2" was released in february, and it ended with a dramatic moment showing anna grabbing a sword from kristoff and swinging it towards the camera. "that [scene] was in [the movie] at one point, and then it was out," chris buck, the film's codirector said. "we were like, 'uh oh, people love that scene.' so we made it work, but it's different." the final version of the anna-sword moment shows her grabbing an ice-sword from a statue instead of a real sword from kristoff.
when elsa sees all the snow memories in ahtohollan, there's a reference to "the little mermaid." elsa sees young iduna ask young agnarr what he's reading, and he replies: "some new danish author." on the cover of his book, you can just make out the silhouette of ariel from "the little mermaid." hans christian anderson was the danish author of both "the little mermaid" and "the snow queen." "the little mermaid" was published in 1837, and "the snow queen" came afterwards in 1844. if young agnarr was reading the "new" book by anderson in 1837 as a boy, then that means the current timeframe in the "frozen" movies could be around the late 1860s or 1870s.
when olaf "dies," his snow is gathered by gale and dotted with purple flowers. this is likely reference to the scene at the end of "frozen" when olaf is finally experiencing warm weather in arendelle and smells two buckets of purple flowers.