The animation is good. Not as good as a todays Pixar or Dreamworks movie but pretty damn good for a Danish production whose budget is definitely much lower.
Major flaws are in facial expressions and in body movements. Ok, they are portraying Danish folks and as that you cannot expect Mediterranean expressions so this is not much of a problem (ok, I am joking but I am allowed to say that 'cause I lived 3 yy in Copenhagen and I love Danskerne).
As for the story it is a revisitation of something already seen but in a very different flavor. The idea could be something a Monster & Co but the development is totally new, to my knowledge.
1 star more than actually deserved because of the effort and the result totally lacking the unbearable attitude of todays American Studios, full of politically correct garbage and hidden (actually not so hidden) ideological inputs (see the fact that it is NOW impossible to have white characters even if the animation movie is set in France during Middle Age, see the very last Live Action Beauty and the beast).