Continuity mistake: When Ellen tells her mother-in-law about her whereabouts in the Indian Ocean, Irene Dunn's hand is held high up on the column, and at the base in the following shot. (00:09:35)
Plot hole: The entire shoe store scene is a mistake. If she truly had larger feet, then she would not have had any shoes in the trunk at home that would fit her, and she would have had to go to the shoe store barefoot...at which point she would have known her shoe size had got larger, and the salesman would not have had to tell her.