When Shrek and Fiona first met Lord Farquaad, they get mad at each other, and Shrek goes back to his swamp. He also gets mad at Donkey, and he returns alone. Later, Donkey shows up, and he points out all Shrek's mistakes and helps him to get back to Fiona. For what they say, the castle is really far away and Donkey calls the dragon, who immediately shows up.
Did Donkey actually go all the way back to the dragon's castle, convince her that they are in love, unchain her and fly back to Shrek's in a few hours? (Since Fiona insisted in get married the same day.) I know it's a fairy tale, but it will be nice to have a canon answer.