The character is portrayed by Eric Millegan and was introduced as Dr. Temperance Brennan's young assistant at the beginning of the series before he received his doctorate in forensic anthropology in season 2.

In the penultimate episode of the series, "The Day in the Life", Zack is exonerated for the murder that left him incarcerated at the end of season 3.

His colleagues conspire to make Addy less comfortable to motivate him to complete his studies, thus encouraging him to fulfill his potential as more than just an assistant.

[2] The episode "The Perfect Pieces in the Purple Pond" reveals Addy is receiving psychological treatment from FBI psychologist Dr. Lance Sweets.

In the Season 4 finale, Zack Addy is considered a suspect when a man is murdered in a popular nightclub owned by Booth and Brennan.

At the end of the episode, it is revealed that the entire thing was in fact a dream about an alternate timeline that Booth had while being unconscious and is the part of a new book Brennan was writing.

Addy consults the evidence files on the puppeteer case and concludes that he committed the crimes while blacked out and wishes to return to the mental institution.

The team at the Jeffersonian finds out that it is instead Addy’s doctor from the institution, Dr. Mihir Roshan, who has been committing the murders and arranging the skeleton marionettes.

Unable to kill Roshan himself, Addy concludes he could not have committed murder under the order of the Gormogon, and confesses his innocence to Brennan and Booth.

[5] In "The Steal on the Wheels," the Jeffersonian team is able to locate the body of the Gormogon's former apprentice, the true killer, and match the blood on it to the lobbyist Addy supposedly killed.

When he discovered Dr. Brennan's own Forensic Anthropology professor had become her lover, Zack repeatedly wondered aloud whether he might enter into a similar relationship with Dr.

"[8] Outside the laboratory, Addy struggles with social interaction and intuition, making him a relatable figure for viewers who may also navigate similar challenges.