Errors made by characters (possibly deliberate errors by the filmmakers): When Miss Margaret Schlegel (Emma Thompson) comes down the stairs and first meets Mr. Bast (when he attempts to retrieve his umbrella), Margarete calls her sister "Helena" and not "Helen". Helena is the real name of the actress portraying the sister (Helena Bonham Carter), and "Helen" is her characters name.
Anachronisms: When Charlie and Dolly Wilcox are hiding from Margaret Schlegel in the castle, the scene closes with low angle wide shot of the castle with a view of the sky behind it, revealing several aircraft contrails. There were no aircraft capable of leaving high-altitude contrails in the time period this movie is set in.