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.
All of Mattis' robbers were played by music people, singers, artists and guitar players, since singing were so integrated with the story.
The evil forest trolls called "grådvärgar" were played by children.
Actor Börje Ahlstedt,who plays Mattis, has confessed that he actually lied about being able to ride a horse in order to get this part. When Ahlstedt arrived on the location, he sat down and wrote "You are great with horses" on hotel stationary for a whole night in order to get the confidence up.