Continuity mistake: When Misty says that she and her friends have to go to Valencia Island, her bag disappears. This also happens at the end of the episode. (00:14:48 - 00:20:53)
Continuity mistake: When Pikachu agrees after Professor Oak says, "That's the spirit!" he is on one tile, but in the next shot, he is on two. (00:11:08)
Answer: He is a good guy but just found himself in a bad situation when he worked for Lysander. He didn't want him to harm Ash and his Pokémon when he was trying to get the special bond between Ash and his Greninja to work. He does leave Lysander and go back to being a good person.