• English / United States: Aaron's Lucario
• Japanese / Japan: アーロンのルカリオ
• Japanese (Romanized) / Japan: Aaron no Lucario
• Japanese (TL) / Japan: Aaron's Lucario

Aaron's Lucario was the Pokémon that served the Hero, Aaron in ancient times. Aaron recalled his Aaron's Lucario into his staff before he went to the Tree of World's Origin on his Pigeot. Years later, Aaron's Lucario mistook Ash Ketchum as Aaron as Ash Ketchum was dressed up in the hero's outfit which looked just like Aaron's clothes.

When Aaron's Lucario was recalled from Aaron's staff in the present day, Ilene explained the situation to Aaron's Lucario. She told him that the events he thought happened yesterday were actually many years ago. She then told him that she knew he had disappeared during the battle near Aldoran Castle. While Ash Ketchum and his friends were in search of Ash's Pikachu, Aaron's Lucario lead the search on the command of Queen Ilene.

Aaron's Lucario had thought that Aaron abandoned him and the kingdom, but it wasn't until Aaron's Lucario reached the Tree of World's Origin and saw a time flower of Aaron that he realized exactly what had happened after he was put into the staff. Aaron's Lucario sacrificed itself so that Mew and the Tree of World's Origin would be preserved.