Factual error: In "Pikachu and Pichu," when Pikachu and the Pichu brothers come to the big play structure thing, there are a bunch of Pokemon around, including a red-and-white, ball-shaped Pokemon called Voltorb. The dubbers for the English version made a very noticeable error here: instead of Voltorb saying "Voltorb," (almost all Pokemon say parts of their names when they speak) it says "Electrode," which is the name of a similar-looking, but different Pokemon. The two are both red and white, but the difference is that Voltorb has eyes on the red part of its body, while Electrode has eyes on the white part of its body.
Continuity mistake: During her battle with Ash, Lisa jumps over a patch of flowers and sends out her Girafarig. During this shot, the flowers are considerably higher than the fence that surrounds them. However, a few shots later, the flowers are seen again, but this time they seem to be lower than the same fence.