Awesome Music: They may be tough, badass robbers, but man, can they sing. Then again, when you're outcasts from society sitting around in a castle, music and theater is pretty much the only entertainment you've got. This was shown prominently in the movie, with musicians being cast instead of actors for many roles. Songs can be found here.
Germans Love David Hasselhoff: Not only did the movie win the 1985 Berlin International Film Festival's Silver Bear, but both the musical and stage adaptation has been written by Germans.
The Fair Folk almost kidnapping Ronia. In the movie, they start making eerie sounds as the mist drags in, whispering "come", and Ronia starts walking in a trance, mumbling "I'm coming..." all the while.
Ugly Cute: The depiction of the grey dwarves is certainly intended to be creepy, but their short stature and flipper-like arms make them resemble baby penguins.
Unintentional Uncanny Valley: Some of the characters have sufficiently realistic enough 3D models that they end up being creepy.