Factual error: When Quasimodo and Esmerelda are on the roof of the cathedral, a piece of the roof breaks off and slides with them standing on it. The material creates sparks as it slides. The material would be either copper or (more likely) lead, neither of which can be made to spark.
Factual error: The statues outside of Notre Dame Cathedral are shown as plain stone, as they appear in modern times, although in the story's period (the fifteenth century) they were polychromed.
Factual error: After Phoebus distracts the guards to stop them from chasing Esmeralda, we see the goat smoking a pipe to give the appearance of a beggar. Tobacco (and consequently, smoking pipe) wasn't introduced in Europe for at least another century, as it's a plant native to the Americas.Friso94