Zachary Uriah "Zack" Addy, Ph.D, is a fictional character in the television series Bones. He is portrayed by Eric Millegan. The character was introduced as Dr. Temperance Brennan's brilliant young assistant at the beginning of the series before he received his doctorate in Forensic Anthropology in Season 2 and became a forensic anthropologist. Millegan was a series regular for Seasons 1-3, appearing in all episodes. Since then, he has made three guest appearances in Season 4's "The Perfect Pieces in the Purple Pond" and "The End in the Beginning" and Season 5's "The Parts in the Sum of the Whole".