This is probably one of the only purely written reviews I will ever do on this site, but as I don't see the need to do a video review on "Frozen Fever," but still want to talk about it, this is what it is. The first part will be spoiler-free while the remainder will dive into more detailed aspects of the short. I'll be sure to mention when I'm getting to the spoiler-y stuff too.
"Frozen Fever" takes place what seems to be a few months after the events of the main film and is centered around Anna's birthday. Elsa, who is choosing to reject the idea that she has a cold, is trying to make this birthday a perfect day for Anna. It's a cute movie and really focuses on how close the two sisters are now that they aren't separated from each other. The song "Making Today A Perfect Day," which takes up most of the run time, works neatly as well and seems to draw on some of the lost ideas the songwriters had while working on the original score. Nearly all of "Frozen's" major characters make an appearance of some sort and there are lot of callbacks to the main film, both in the lyrics and in character actions (Sven getting his tongue stuck to ice). As a fan of "Frozen," I really enjoyed this short and had a smile on my face the entire time I watched it.
Now to dive into some specifics. One thing which honestly surprised me about the short is how close Elsa came to death (again) by almost plummeting off of the clock tower in a feverish haze. In fact, her whole demeanor during the thirty seconds or so leading up to that reminded me of someone in something of a drunken or high stupor, which, while I applaud the writers for putting in, seemed a tad dark for what I thought would be a short, fun, non-life threatening return to Arendelle.
Another bit which is worth pointing out is Elsa's powers. It would seem that she also possess some form of, in Anna's words, "tropical magic," as she gives both her and Anna a very non-ice makeover. Maybe this is just another callback to the original, but it seemed slightly odd unless it was a very, very unique form of ice. It would also seem that the creators decided to bring back the fact that Elsa can create life on a whim, with each of her sneezes creating little snow creatures. We saw this in the original with Olaf and the giant snowman, but those were more or less intentional creations. It'll be interesting to see what else Elsa's powers are capable of with the sequel.
The other bit I must comment on is the ending with Hans. I simply had to laugh at the fact that he's stuck in the Southern Isles shoveling manure and then gets hit by a giant snowball, courtesy of Elsa. Again, a great callback and had the theater I was in laughing.
One last thing which I want to mention is when Kristoff shouts "I love you, baby!" It was a really cute part, especially when followed by a reassuring "I do." Plus, it definitely shows that some time has passed since the main film since I don't think they were quite at the "I love you" stuff yet.
As is evident, I really enjoyed this "Frozen" short and had no real issues with it; only some questions which will hopefully be answered in "Frozen 2," whenever that decides to come out.