Continuity mistake: Jack tells Cinderella that there's a new guest and she picks a yellow jacket, a blue piece of fabric and a pair of shoes. In the following shot the shoes disappear from her hand, and a shot later the jacket and the fabric also vanish.
Audio problem: When Cinderella wakes up and sings she walks behind a screen singing "Tadam dam tadee" but her mouth isn't moving.
Continuity mistake: After she wakes up, Cinderella walks behind the screen and a girl-mouse commands the others to get inside a plank. The girl-mouse stands in front of the gap between two planks. A shot later she's now behind the gap.
Continuity mistake: Cinderella wakes up to the clock's chime and pushes the duvet to the foot part of the bed. In the following shot the way it's folded changes, and a shot later it's now magically covering almost all of the bed.
Continuity mistake: After Cinderella picks up her dress from the trunk the mice standing on the lid change positions: From purple, yellow, blue and red, to light red, yellow and turquoise blue. Change of colour of the dresses might be due to lighting.
Answer: Cinderella's entire outfit was magically created by the Fairy Godmother. Not only was the spare shoe Cinderella had in her possession identical to the other one, it likely would be charmed so that she is the only one who can wear it. It's similar to young Arthur being the only person who could pull Excalibur from the stone because he was the true king. No other woman who attended the ball wore glass slippers. If they had, they'd be able to also produce the spare shoe as proof.
raywest ★