In the last book of fnaf3, toy bonnie went into a empty suit and became spring trap. But the suit controlled him and turned him into a completely different animatronic. He even forgot who he was.

Huh???!!!Who are you???

I am spring trap of course!!!

Everybody shall fear me!!

Well, I don't know anyone named spring trap. Maybe the puppet will take a look at you.

Fine.

So Phantom Freddy took SpringTrap to the puppet's room. That's one of the rooms that is burnt.

Uhh...Marionette???Are you okay??

Hm?

You have been acting like this since the day of the fire!!!

Huh??Fire???

Yeah!A fire swept through the entire pizza place.It even killed a old friend,Toy bonnie!!

After spring trap heard what phantom freddy said, memories of that day flooded into his mind.He suddenly remembered him dying....the nightguard calling the fire departememt....and his friends badly burnt.

Wait...Toy bonnie...fire....Uhhh!!!!

Uummm...are you okay?