Clarissa's Dialga

 Clarissa's Dialga   is a Pokémon she obtained in Sinnoh as a  Legendary Guardian.

Sparks: Diamond and Pearl
Clarissa caught Dialga at The Spear Pillar to aid her in the battle against Team Galactic. When Cyrus opened the portal to the Distortion World, Katrina went through despite Clarissa, Mason, and Cynthia's warnings. Clarissa used Dialga, Mason used Palkia, and Cynthia used Cresselia to chase Katrina and Cyrus before he reached Giratina. All three were sucessful but Giratina was enraged by Cyrus and attacked them. Dialga attempted to fend the Renegade Pokémon but was hit by an Earthquake.

Sparks: Black and Whire
Dialga is seen visiting Clarissa when she returned from Unova.

Personality
Unlike many of Clarissa's legendaries, Dialga goes out of his way to visit the girl and is quite fond of her.