Why Lucas in the diamond and pearl series?

It seems you're asking about "Lucas" in the *Pokémon Diamond and Pearl* series. However, there is no character named Lucas in these games.

Perhaps you are thinking of:

* Lucas: The male protagonist in the *Pokémon Black and White* games.

* Barry: The rival character in *Pokémon Diamond and Pearl*. He's known for his competitive nature and strong friendship with the player.

* Dawn: The female protagonist in *Pokémon Diamond and Pearl*. She's the player's rival and a strong trainer.

Please clarify who you're asking about so I can give you the information you need!