Enter Those Three! Referee School Island! - S7-E52
Continuity mistake: When Serena meets Jimmy at night, Jimmy's sleeves disappear. This also happens when she tells him to not give up. (00:14:12 - 00:16:44)
Enter Those Three! Referee School Island! - S7-E52
Continuity mistake: When Ash, Max, May, and Jimmy ask, "Huh?" the visor on Ash's hat goes from red to black. (00:16:47)
Enter Those Three! Referee School Island! - S7-E52
Continuity mistake: When Wartortle starts evolving, the collar on Jimmy's shirt changes from black to green. (00:17:44)
Enter Those Three! Referee School Island! - S7-E52
Continuity mistake: At the end of the episode, the brown lining on Brock's sleeve turns orange. (00:20:47)
Enter Those Three! Referee School Island! - S7-E52
Continuity mistake: When Jimmy notices the Magikarp in his flashback, his bag disappears. In the same shot, the white fin on the Magikarp turns yellow like the rest of its body.
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.