Lucas is the playable male protagonist in Pokémon Diamond, Pearl, and Platinum. His female counterpart is Dawn. In the manga his name is Diamond and his Starter Pokémon is Turtwig. Furthermore, his Diamond & Pearl outfit closely resembles that of Ash in the series. Lucas also appears with the name 'Hareta' in the manga series 'Pokemon Diamond and Pearl Adventure', starting out with a Piplup, he was raised by Pokémon. His rival is Jun (Barry).
Lucas also had a brief cameo in the opening of Giratina and The Sky Warrior, battling Brendan. In addition, concept art for Lucas' anime counterpart exist, suggesting Lucas was to play a bigger role in the main series, but this never materialized, most likely because a voice actor couldn't be found.