Serena Becomes Satoshi! The Ultimate Pikachu Showdown!!.During their journey to Snowbelle City, Ash gets terribly sick with a cold after a night of intense training. As Clemont and Bonnie try to find some medicine, Serena is forced to stay behind and nurse Ash back to health. But unfortunately for her, a trainer with his Pikachu appears and challenges Ash to a Pokémon battle. Not wanting to burden her dearest friend, Serena decides to take action and battle in Ash's place while Ash's Pikachu helps her.