In the Scyther episode, Jessie's hair was cut, but after a few scenes, her hair was there again.
In 1 episode, Eriko was taller than Toshiko, but the other way round in the next episode!
The first purple Jynx scene, (unappropriate for children) they drew the br@ wrongly, meant to be tipped at the top but curved at the bottom, whilst drawn tipped at both sides.
In episode "Psychic VS Ghost, Night battle", Alakazam was drawn even shorter than Ash! (Alakazam meant to be 1.5m tall, Ash approximately 1.4m)
In episode before "Psychic VS Ghost", May mentioned about a Chinese restaurant selling noodles. But the noodles AND the restaurant look 100% Japanese, and 0% Chinese.