Holly's Father is a character in the Monster Rancher anime series. He is the unfortunate person who unlocked Moo's soul by accident, mistaking it for the Phoenix's Mystery Disc.
Season 1
Several years before the series begins, Holly's Father married an unnamed woman and had a daughter, whom they named Holly. It is assumed that his wife's death is part of what started his downward spiral.
Later, he was banished from the Tochika village because he allegedly lost an election for village leader, and decided to find the Phoenix without the aid of the magic stone. In reality, his power over the magic stone worried the village elders, who believed it would bring disaster to their village. In the end, they were right. For years, Holly's father searched for the Phoenix's disc to no avail, until his search led him to the Valley of Darkness. There, he found Moo's soul in a form of a Pandora Disc. However, it turned out to be a trap, as Moo needed a host in order to reunite with his old body. Moo took possession of his human body, changing his form into a giant armored being. From there on, he was helpless, trapped within his own consciousness as Moo used his body and memory to terrorize the entire world.
Season 3
After Moo’s Dragon form was destroyed by the Phoenix, both Holly's Father and Moo’s soul were trapped within a Dark Disc . Holly eventually finds the disc and goes on a quest to use the magic stone to unlock her father once again, but the Searchers soon realize that his soul is battling Moo's within. Despite this, they manage to free him at the Shrine of the Ancients, but they find that his memory has been erased to the point that he doesn't even recognize his daughter anymore.
Genki tries to convince Holly that her father’s memory will return, but Hare and Tiger are worried that if they heal him of his amnesia he will never forgive himself for the evil deeds he has done. Just then, they are ambushed by Durahan and his minions who are hoping to use Moo's soul as a source of power. Instead, Moo uses their energy to unlock himself, and they merge into a giant being called Ruby Knight.
Moo's resurrection draws Holly's father back to the Shrine, where Moo's words as he mocks the Searchers restores his memory. He is finally able to embrace Holly, knowing who she is. Holly’s father then turns on Ruby Knight, realizing that Durahan’s team is suffering the same fate as he did. Holly is worried that Moo will reclaim her father once again, but her father ventures inside Moo's mind and is able to communicate with Durahan. Together, they realize that only the Phoenix's soul will break their evil bond, and they ask Genki to merge his team into the Phoenix once more, destroying Moo's soul once and for all and turning Durahan and his team into Goodies.