He and show creator Janet Tamaro have known each other ever since Tamaro's first TV job at Inside Edition, where they worked together. O'Reilly is also friendly with Rizzoli star Angie Harmon, an outspoken conservative.
The Fox anchor brought his daughter to set last year and toured the show's autopsy room. "He took one look at the autopsy table and said, 'Yeah a lot of people would like to see me on that," Tamaro tells TV Guide Magazine. "I said, 'Well, how about you come back and do a guest spot.'" O'Reilly is expected to film in July for an episode that will air at the end of summer.
Season Two of Rizzoli & Isles begins July 11.