Serena is a character appearing in Pokémon: Advanced Challenge.
Pokémon the Series: Ruby and Sapphire
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.