Director Tage Danielsson read aloud from Astrid Lindgren's book every morning, preparing the cast and crew for the part that was to be filmed. "It felt like we were carrying Astrid under our jackets for the whole day", Danielsson said.
When filming the scene where the robbers run out in the snow naked to clean themselves, two big portable saunas were rigged inside the castle set. The actors sat in the saunas and on cue, when cameras rolled, opened the doors and ran off into the snow.
The first Swedish movie ever to use CGI: hand-painted renderings of the terrifying vultures called vildvittror.
The evil forest trolls called "grådvärgar" were played by children.
All of Mattis' robbers were played by music people, singers, artists and guitar players, since singing were so integrated with the story.