Cortana from Halo
No matter how you tell the differences between a hero and their sidekick, no video game blurred the lines like the Halo series. The world will forever remember Master Chief as the face of the franchise, but those who played it know that while the armored space marine may have brought the power, it was his onboard AI Cortana who provided the plan. Artificial intelligences are nothing new to sci-fi, but in gaining access to the Chief’s brain, Cortana became more than just a partner, the two became a single soldier. Since players only ever controlled the Chief, Cortana fell into the sidekick role quickly, but by the time Halo 4 came around, players knew the partnership was one for the ages.