These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Green Aesop: István Fekete's general intended aesop "Respect nature, strive for balance, but know that nature can be cruel and killing/death is unavoidable." is also in effect here. Not that idealistic or family friendly but still green.
Moral Event Horizon: The hunter crosses it when he kills Vuk's entire family early in the movie.
Nightmare Fuel: Many characters (even developed ones who had several lines) get not only killed, they are also eaten by our main protagonists. One scene has the title character devouring a duck 'till only its head remains. At no point are they drawn realistically — everybody you see getting mauled is an honest-to-goodness cartoon character. Thankfully explicit Gorn is avoided, however.
One-Scene Wonder: Most of the rather entertaining and memorable animal characters Vuk encounters (such as Szú, the grumpy hedgehog, Unka, the lovesick frog or Nyau, the feral cat) appear in exactly one scene in the movie, then are never even mentioned again. This shows that there's a big forest out there with many colourful inhabitants. Some of these characters are Cross Overcameos from István Fekete's other novels, such as Hú the owl, who stars his own book.
Special mention needs to go to the two geese, who provide the funniest scenes of the movie.
Sequelitis: The second one, made in 2008, is pretty much the complete opposite of the original.
So Cool It's Awesome: The original is not only considered a great animated film; it is considered one of the best ever made.