Factual error: In the whole episode, Romania is depicted as a monarchy with the king in a position that allows him to make political decisions. However, Romania ceased to be a monarchy in 1947. By the time depicted in the episode (circa 1997), Romania was a republic and its head of state was the president. Members of the ex-royal family did not hold any positions in the Romanian government and were certainly not authorized to represent Romania in international events.
Attack Of The Mutant (1) - S2-E2
Other mistake: In part 2, it was revealed that Libby was really the Masked Mutant all along but, in one scene in this episode, Libby is sitting next to Skipper while the Masked Mutant is standing on top of the bus.
Through a Lens Darkly - S1-E20
Continuity mistake: At the end of the episode, Tom is absolutely drenched because the car has crashed into a river, and he has to wade through the river to get to the riverbank. However, as he walks away, he doesn't leave a single wet or muddy footprint behind him despite this.