The Magic Mirror presented Farquaad with 3 options for princesses to marry to become King, Snow White, Cinderella and Fiona.
Fiona was locked in the Dragon’s Keep (obviously) and Snow White was seen in Shrek’s swamp with the 7 Dwarves and the other fairytale creatures.
But where was Cinderella during this film? If Lord Farquaad chose her, where would he go get her?