Revealing mistake: Cary Grant shows off his ice skating moves but you can tell it's a stunt double. The double is a bit shorter than Grant. Also in the same sequence, the two other skaters have noticeable doubles as well.
Revealing mistake: As Lulu is pulling her fishing pole out of the school steps, you see if you watch closely that the pole actually passes through the concrete of the steps rather than her lifting it over. (00:02:00)