Continuity mistake: In the camp cabin, the two girls are talking. It cuts away from one girl, and she has an ice cream cone in her hand, then cuts back and it's gone. This keeps happening.
Trivia: For the scene when the camp girls are following the twins to the cabin Miss Inch was putting them in, the director wanted the girls to march like soldiers. The girls could not march very well, so he just decided to leave it as it was. The whistling the girls do is not the girls' whistling--its a recording of the march from Bridge on the River Kwai.
Trivia: Hayley Mills had one stunt double that can be seen in the movie when one of the girls has her back to the camera or when Hayley is doing something she can't do by herself. The stunt double girl received a Duckster award for the best unseen performance by an actress - only three have ever been awarded.
Mitch Evers: Would you mind putting on something decent?
Margaret 'Maggie' McKendrick: I'm dressed perfectly decent.
Mitch Evers: Yeah, running around in my bathrobe. The priest could come in here any minute, it looks like we just.
Margaret 'Maggie' McKendrick: Like we what?
Mitch Evers: Just go upstairs and put on some clothes.
Verbena 'Ever's Housekeeper': You didn't know what a good thing you had when you had it.
Mitch Evers: Huh?