The Double Trouble Header - S3-E2
Continuity mistake: When Ash uses his Pokédex to find facts on Chikorita, the end of his right index finger is on its left side, but in the next shot, it is not. (00:02:01)
The Double Trouble Header - S3-E2
Continuity mistake: When Pikachu notices Casey and Chikorita, the part of Ash's jacket to the right of his right strap excluding the sleeve goes from blue to white and then back to blue. (00:01:26)
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.