Continuity mistake: The pony pulling Ditchwater Sal's cart changes throughout the movie. This would be so as to not overwork any one animal. It is most noticeable in the scene when Una is driving the cart after Yvaine. When she is in the city, the pony has a white stripe all the way down its face; when it is galloping in the forest, it has two separate white spots on its face; and the pony that Tristan detaches from the cart and rides has one spot on its face. Also when Tristan detaches the pony, it only has on riding gear (a saddle and bridle), whereas earlier in the scene it only has on a harness for pulling the cart.
Continuity mistake: When Lamia fakes crying and pretends to let Tristan and Yvaine go, the back of her dress changes slightly. When she first turns round, through the criss-cross at the back, you can see the goldish coloured fabric. But in the next shot, the gold is gone and all you can see is black.