Hanna Zetterberg, who played Ronja, got the hard wooden bed featured in the movie as birthday present during shooting.
Vargklämman is snowed in, not a robber will get out all winter.
Ronja: Snowed in? But how am I supposed to meet... I mean, how am I supposed to get out into the woods?
Mattis: You won't get there until spring comes, Ronja mine.
Lovis: What a nuisance. Twelve snowed in ...
At one part in the film, Birk sneaks over to "Mattisborgen" to meet Ronja in the basement. This is impossible because of the gap between the two castles which is obviously too deep to have a basement below.