 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.Millegan was a series regular for Seasons 1 to 3, appearing in all episodes.Since then, he has made guest appearances in Season 4's "The Perfect Pieces in the Purple Pond" and "The End in the Beginning" (dream sequence), Season 5's "The Parts in the Sum of the Whole" (flashback) and returned in the Season 11 finale "The Nightmare within the Nightmare", and had a recurring role in the series' final season.