Continuity mistake: At the end of the first season Tohru had kind of changed sides. Then in season 2 he was a bad guy again until the 4th episode where he became good as if the previous episode was out of order.
The Tiger and the Pussycat - S1-E12
Continuity mistake: When Jade cracks the shades Dark Jackie is wearing, he drops first the glasses and then the Talisman case right on top of the shades, damaging them further. But later, when Tohru picks up the case, the shades are gone from beneath it.
Continuity mistake: The first four episodes of season two have absolutely no continuity with the show. Prime examples are the fact that Shendu exists again as a statue which had been confirmed to be destroyed in "The Day of the Dragon", the final episode of season one. Next during "The Warrior Incarnate" it is mentioned that not all the talismans were in fact present, such as the dog talisman, when all talismans must have been found, or the events that escalated during the final episode of season one would never of happened. This problem is the extended during the next episode where Jackie Chan discovers the snake talisman in some sort of Brazilian temple - he had already learned of the snake talisman by stealing it from the museum quite early on in season one. The final continuity error is that Tohru goes from friend to foe and then back to friend as if the first four episodes of season two never happened.
Suggested correction: These were "flashback" episodes, not "they never happened" episodes.
Tale of the Demon Tail - S2-E19
Continuity mistake: In the scene where Jackie fights Shendu/Valmont and Ratso (just before Ratso lands in the cookie factory), the spellbook collection the villains have brought up to the tank's top earlier on is nowhere in sight now.
Continuity mistake: Ratso throws the Babylonian urn at Jackie; Jackie catches it and ends up sitting in a chair, putting the urn right beside him. But when Finn and Ratso attack him with the scimitars, Jackie is found still sitting in the chair, but the urn has vanished.
Continuity mistake: When Tohru arrives at the McDonald farm, he tosses his former Enforcer buddies into the water trough where Daolon Wong has been landed by Jackie: first Chow, then Finn, and lastly Ratso. But the threesome land in the trough in the following order: Finn, Chow, Ratso.