In "Power Rangers Operation Overdrive," Andrew Hartford's transformation of his son Mack into a human-android hybrid is explained through a backstory that is introduced in the series. After Mack fell off a cliff in a tragic accident, Andrew Hartford, a brilliant inventor and a wealthy businessman, used advanced technology and robotics to rebuild his son.
Andrew, driven by grief and desperation to save Mack, integrated cybernetic enhancements into Mack's body, effectively turning him into a powerful android while preserving his human consciousness and traits. This process allowed Mack to possess superhuman abilities that are typical of Power Rangers, including enhanced strength, agility, and resilience.
The transition from his original form to the half-human, half-robot form is not thoroughly detailed in the series, but it emphasizes themes of loss, love, and the lengths a father would go to for his child. As the story unfolds, Mack's dual nature plays a significant role in his character development and the challenges he faces throughout the series.