Jimmy met Serena when he accidentally arrived on the island because he was sleeping on a boat. Much later, he introduced Ash and his friends to her when they accidentally boarded the boat to Bomba Island instead of the one to Mossdeep City. Brock immediately fell head over heels with Serena, but Max stopped him from flirting with her by dragging him away by the ear. Serena then agreed to enlist Ash and his friends as helpers to students who were training to become battle judges. She assigned Jimmy to become the judge of a mock battle between Ash and Brock. During the battle, Serena noticed that Jimmy made many mistakes with the judging, such as when Jimmy mistook Corphish for being defeated when in fact, it just fell down for a few seconds. She explained to him that he was still learning and was expected to make a few mistakes every now and then.
Later, after Jimmy told his story to the group about the time he got Wartortle, Ivysaur, and Charmeleon, Serena returned and talked to Jimmy. She noticed Team Rocket approaching with a mecha, which they used to capture Jimmy's three Pokémon. Jimmy attempted to free his Pokémon, but he was thrown off the mecha and became disheartened. Serena noticed this and told him about his good heart, which renewed Jimmy's faith. After Team Rocket was defeated with the help of Jimmy's newly evolved Blastoise, Serena told Jimmy that he should become a Trainer instead of a judge. The next day, Serena and Jimmy waved farewell to the group after Brock flirted with her once again.