SB2: You explore the Pizzaplex (again!) and discover how Fazbear Ent. got the funds to build this 1,000,000 square foot mall even though they were a failing pizza chain just a few years ago.

William Afton is the final boss (again!) and it's worse than ever before: it turns out that William Afton is a get rich quick guru! and he tricked everyone in the world into paying for the Pizzaplex's construction.

You have you outwit him in the stock market which all takes place in a quicktime event. All the stock calculations overheat the springtrap suit's computer, and he bursts into flames and explodes.

Gregory turns around yelling "WE DID IT, FREDDY!" But then Freddy's eyes turn purple and he says "I always come back."

The screen goes black.

SB3: While running away from Afton-Freddy, you discover that EVERY FNaF building is below the Pizzaplex.

Turns out William pulled a Voldemort and made every animatronic a horcrux. You have to explore each pizzeria and destroy every animatronic.

William is still possessing Freddy and you don't want to destroy him, so Gregory builds a giant mech out of all the animatronics, and like Undertale, the souls of the murdered children come down to help you. In another quicktime event, you metaphysically punch William Afton so hard he clips into another plane of existence. William is finally gone forever.

SB4: Turns out you punched William into the wrong plane. He's now God. He turns everyone into furry OC animatronics except for Gregory. It's a living hell.