Zatch Bell! (US)

Zatch Bell is about a boy named Kio. On his birthday, his father sends him a rather strange present. A little "boy" named Zatch, with weird powers. They soon discover that Zatch is no normal boy, but a Mamoto, a being from another universe. Every 1000 years, Mamotos go to Earth to find partners to help them battle other Mamatos for the spot as King of the Mamoto World. Now Zatch and Kio are in the running as well, beating every Mamaoto that comes their way, and learning more about themselves, and each other along the way