You watch Bones weekly you have wondered why Eric Millegan was out of the series for a while?

Eric Millegan, who played Dr. Zack Addy on "Bones," was absent from the series for a period due to a combination of storyline decisions and his own personal challenges, including mental health issues. His character was written off after Season 3 but returned in Season 10 for a few episodes. Millegan has since been open about his struggles with Bipolar disorder, which contributed to his time away from the show. His return was well-received by fans, highlighting his significant role in the series.