I'm pretty sure everybody knows that Golden Freddy and Springtrap are two different animatronics and have no history together whatsoever, or do they?
There has been evidence from the FNAF 3 minigames that show a part of the Freddy Fazbear pizzeria that we have never seen in the first two games, with both Golden Freddy and Springtrap in physical working condition
But, could this be the original Freddy Fazbear's pizzeria 30 years before Freddy Fazbear himself?
"Angel, why do you think this? Your making no sense"
Or am I? Have you ever heard the FNAF 3 fan made song "It's time to die"? Well if you have and actually listening to the lyrics, the artist interpertating Springtrap sings "30 years since all this happened". As you can clearly see, the underlined words are in past tense, which could mean that something must've happened 30 years ago that could of affected the original restaurant, which has been given the popular name in the FNAF fandom, "Fredbear's Diner".
Also, in Night 5 of FNAF 3, something happens to the building itself, setting it on fire, what if the same thing happened 30 years ago? According to the newspaper in Night 5 of FNAF 3:
it states that "a local attraction based on an ancient pizzeria chain burned down overnight." It also states that "Very little was found at the scene. The few items were salvaged will be sold at a public auction."
So, to the main point of this theory, the article states that the restaurant Freddy Fazbear's pizzeria is a somewhat tradition, for it stating that the pizzeria is ancient and part of a chain of other generations of the restaurant itself.
So, the very first restaurant that started the chain must've been Fredbear's Diner, which would include the first animatronics of the first generation, FredBear and Springtrap.
Golden Freddy and Springtrap were animatronics of Fredbear's Diner.
"Angel, Springtrap wasn't included in the first or second game, how could this be possible?"
Back to the fire in Night 5, as I've said the fire must've happened 30 years ago, the start of the pizzeria's generation, the only animatronics that survived were Golden Freddy and Springtrap, there were most likely a "Golden" Foxy and "Golden" Chica, as in the first two games there are 4 main antagonists, but most likely the original versions of Foxy and Chica were destroyed in the fire, according to the article it states that few items were found, which would indicate Golden Freddy and Springtrap's survival. When Fredbear's Diner burned to the ground, it was rebuilt as Freddy Fazbear's Pizzeria, and Golden Freddy and Springtrap were put out of order and stored as the generations of the pizzeria and the animatronics expanded over the years.
"Okay Angel, then how come Golden Freddy pops up in the first and second games?"
The answer is simple, in the FNAF 2 minigames, "Purple Guy" murdered the well known children of the FNAF fandom that possess the animatronics,
one of the spirits of the dead children found themselved possessing a Golden bear animatronic suit out of wandering around the pizzeria and "revived" by, yours truly, Marionette.
Which is why in both games Golden Freddy shows up in your office as a "hallucination", referring to what I said before about Golden Freddy and Springtrap being stored away.
30 years later, after Freddy Fazbear's pizzeria officially closed it's doors and the new horror attraction has been opened, all of the animatronic suits were used as props for the new attraction, espescially the Fredbear suit, which would be Golden Freddy.
"But how did they use Golden Freddy if he's been stored away?"
A member of the staff must've found the empty Golden Freddy suit in the storage room and took it apart to use it as a prop-
"Then how did they find Springtrap?"
Calm down, I'm getting to that.
As I was saying, the same staff member must've gone back to the storage room at a different time period (I'm guessing a week or more later) and found the empty Springtrap suit, which is when "Purple Guy" comes back to the same location now replaced with the horror attraction to "look around and remember", which is when the children's spirits come out and scare "Purple Guy" into stuffing himself inside the Springtrap suit, doing so the spirits also stuffed inside an endoskeleton, crushing "Purple Guy" to death during the process.
"This doesn't explain why Golden Freddy and Springtrap are original animatronics"
I'm also getting to that.
As you can see here
Both the Freddy Fazbear and Bonnie animatronics are golden, which would show the point that they are both Golden Freddy and Springtrap, it also shows the original restaurant when it first started, because Golden Freddy and Springtrap are in "brand new" condition and do not appear damaged whatsoever. Which could indicate that they were functioning at a period in time, before the fire.
To conclude my theory, Golden Freddy and Springtrap are the original animatronics because there is solid evidence that both were functioning at an established pizzeria for kid's birthday parties at a period of time, most likely before 1987.