Hook appeared at Bristol Crown Court and pleaded guilty to ten charges which included allowing the Labrador to penetrate him.
He was told he had a significant risk of going to prison, the Bristol Post reports.
Judge Mark Horton bailed him for further legal preparation, pending a projected two-hour sentence on August 11.
Hook declined to comment as he left court.
He pleaded guilty to three charges of making indecent images of children as well as possessing extreme pornographic images.
He also admitted having intercourse with an animal, two charges of distributing indecent images of children and three charges of publishing an obscene article.