Continuity mistake: When Misty says, "I wouldn't be surprised if the next gym leaders are tougher than the last ones," the right strap of Tracey's rucksack is on his collar, but in the next shot, it is not. Also, the marks on Ash's cheek go from looking like zs to looking like two pairs of lines. Additionally, his mouth is open, but in the next shot, it is closed. (00:01:42)
Continuity mistake: When Tracey wonders why everyone is outside the museum, the black straps on his bag turn orange, like the rest of the bag. (00:05:29)
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.