Freddy was considered one of the newest animatronics added during the "Great Expansion"(William), along with Nightbear and the Plush Animatronics. He was based off Fredbear to the point where they even share a similar first name, Fred and Freddy. Really however the model was based off the third iteration "Springlocks", the at the time safest "Springlocks"

Freddy had a tendency to want to go towards sources of power, let that be your office where it can "feel" for a lack of better terms, the energy, or the Kitchen, where the generator is located.

The "Springlock Actor" for Freddy was one of the co-owners of Fredbear's Entertainment, Edwin R. Murray. Although Edwin suffered from outside obstacles he always managed to put on his suit to make the kids smile.

Regarding the placement of Freddy on the mainstage and removal from Nightbear stage, for more info on Fredbear's removal please review his page.
Freddy was placed on mainstage due to the Bite, being a replacement to the now in-storage Fredbear animatronic. Making Nightbear a solo act.