Serena is a character appearing in Pokémon: Advanced Challenge.
Season 7: Advanced Challenge
She teaches at the institute located at Bomba Island. She had the student named Jimmy. Jimmy met Serena when he accidentally arrived on the island while sleeping on a boat. Per her request, Ash and Brock had a battle, while her students watched the battle. Jimmy was the referee, who made a mistake by declaring Ash's Corphish unable to battle, since it stood up a moment later. Serena told Jimmy he should have more confidence in himself, as he made the judgement too early. Later on, Serena visited Jimmy and told how he has a big heart and a bond he shares with the Pokémon. Team Rocket snatched Jimmy's Pokémon, so Serena pointed out Jimmy should save his Pokémon, as those Pokémon recognized Jimmy with a kind heart, who should forge his own destiny. Jimmy understood that and managed to have his Wartortle evolve into a Blastoise and rescue Ivysaur and Charmeleon. After the battle, Serena decided to expel Jimmy, feeling he has more potential to become a trainer than a judge. Jimmy understood that and promised to battle Ash, a battle Serena wanted to be the judge for. In the end, Jimmy and Serena bid the heroes farewell and wished Ash luck in his next Gym Battle.