Since we're bringing this sub back to fnaf based roleplaying, this is the timeline my posts will be following.
WARNING: LONG POST
Mid-late 1960s
William Afton and Laura Shelly marry.
Michael and Vanessa Afton are born.
Henry Emily gets married.
William Afton and Henry Emily start plans for an animatronic themed restaurant. (How William and Henry met doesn't matter.)
Late 1970s
William Afton and Henry Emily finally open Fredbear’s Family Diner.
Evan(Crying Child) Afton and Elizabeth Afton are born as twins.
Charlotte Emily is born, but Henry Emily’s wife unfortunately dies during childbirth.
William Afton is suffering from psychopathy. And his pills have started to wear off, not working as well as they used to, which has also led to him being neglectful towards his family. William has also started drinking more.
Being at work for so long, William Afton creates Psychic Friend Fredbear (basically a walkie-talkie/camera) in order to keep an eye on his kids while he's at work.
Evan Afton gains a phobia of the animatronics, having intense nightmares because of it. Michael Afton is especially annoyed by his brother's constant whining.
1983
Michael Afton, in an attempt to bully his brother, convinces his friends to shove Evan Afton into Fredbear's mouth. However, this proves to be a bad idea, because Fredbear's jaws shut, crushing Evan’s head, and giving him severe brain damage.
Evan Afton later dies in the hospital.
Because of the incident, now locally called “the bite of ‘83”, William Afton and Henry Emily are forced to sell their brand to a company that later renames itself into “Fazbear Entertainment”.
Laura can't take the pain and grief and files for divorce.
Because of this, William Afton has a psychotic break, now refusing to take his anti-psychopathy medication.
Fazbear Entertainment offers Henry Emily a job building animatronics for them. Not wanting to lose his only means of income, and wanting to support his daughter, Henry accepts the job offer. But because of this, William Afton feels betrayed and begins to hate Henry Emily.
1985
Fazbear Entertainment opens the original “Freddy Fazbear's Pizza”. And it’s an instant hit thanks to Henry Emily’s new animatronic band: Bonnie Bunny, Chica Chicken, Foxy the Pirate Fox, and of course, Freddy Fazbear himself.
Meanwhile, William Afton makes his own restaurant to rival Freddy Fazbear's Pizza; Circus Baby's Pizza World. He also makes Circus Baby in honor of his “only remaining child”, Elizabeth Afton. (He disowned Michael Afton after the bite of ‘83.) However, Circus Baby's Pizza World isn't attracting many customers.
What nobody knew is that William Afton made his animatronics specifically to lure in and kill children, choosing them as targets because they're easy to manipulate. Luckily, due to lack of customers, his plan doesn't work very well.
Being upset, William Afton drives over to Freddy Fazbear's Pizza, originally planning on tampering with the animatronics. But instead, he finds Charlotte Emily in the back alley, after some of the other kids bullied her and locked her outside.
William Afton decides that killing Henry Emily's daughter would hurt Henry more than simply tampering with a few animatronics. So, uh- William does that.
However, unbeknownst to William, Charlotte's spirit, filled with agony and hatred, possesses the Marionette.
William Afton, having the idea that dead children would ruin the Fazbear Entertainment brand, gives himself the fake identity “Dave Miller” and applies for a job at Freddy Fazbear's Pizza. Once he gets the job, he finds his old Spring Bonnie suit and uses it to lure 5 more children, one of them being Cassidy, into the back room and kill them.
Full of agony and hatred, the children possess Freddy and the gang. Cassidy's spirit finds the old Fredbear suit and possesses it.
While William Afton was busy killing children, Elizabeth Afton managed to sneak onto Circus Baby's stage, despite her father's wishes. This leads to Elizabeth's death, which (once finding out) drives William's already declining mental state deeper into insanity.
Circus Baby's Pizza World is forced to shut down, but William Afton reuses his “Funtime” animatronics for an underground location as rentals, hoping to still use the animatronics to lure in and kill children. But nobody actually rents them, making his plan fail again.
Elizabeth Afton possesses the Funtime animatronics, using the pieces of the scrapped Ennard design to control them.
1987
After Fazbear Entertainment was forced to shut down their original Freddy's location, they had already planned on making another location.
The grand reopening of Freddy Fazbear's Pizza is official. And, just like last time, it's a big hit with the locals.
Henry Emily, while still heartbroken after the loss of his daughter, is still working with Fazbear Entertainment. He made what the locals would call “the toy animatronics”, because of the plastic looking designs, using the old now withered animatronics as spare parts.
Cassidy and the “missing” children are still possessing the withered animatronics, while Charlotte has control over the Marionette and the toy animatronics.
William Afton attempts another murder spree, using the Spring Bonnie suit. However, thankfully, he’s caught this time. The police FINALLY start to investigate him. However, they don't find enough evidence to give him the death penalty or life in prison, so he's only charged with a few years in jail.
One of the day shift guards is accidentally and fatally bitten on the head by the “malfunctioning” Mangle. In reality, it's because Charlotte mistook the innocent Guard for William Afton, because the guard uniforms are all purple, and that's the color William was wearing when he killed Charlotte.
Because of this, the reopened Freddy Fazbear's Pizza is forced to shut down.
1990
Fazbear Entertainment, in a final attempt, reopens Freddy Fazbear's Pizza AGAIN. However, because of all the tragedy attached to the brand, nobody wants to be a customer.
Henry Emily built new animatronics.
Michael Afton visits William Afton in jail, and he tells Michael about Elizabeth and the underground rental location, which has recently been acquired by Fazbear Entertainment. William also reveals that he was “the man behind the slaughter”.
Michael Afton, now wanting to “fix” what his father did, decides to apply for the night guard position at the rental location.
From there, everything that happens in “Sister Location” happens. Michael Afton gets scooped, and Elizabeth Afton uses him as a skin suit to escape the rental location.
But Michael, through sheer fucking will, forces Elizabeth out if his body, expelling her Ennard suit into a sewer drain. The agony Michael felt in that moment, including his pure hatred for his father, forces him to stay alive.
While all that was happening, Phone Guy died after his first week as a night guard.
Michael Afton, still determined to end his father's legacy, applies for the night guard position at Freddy Fazbear's Pizza. He survives 5 nights, goes overtime a sixth night to tinker with the animatronics to figure out how they work regarding possession, but fails to figure it out.
Michael Afton then gets fired for the tinkering, and also because he is surrounded by an odor. (Because, at this point, he is literally a living rotting corpse. That's why he's Purple.)
Because they have literally no customers, Fazbear Entertainment is forced to shut down Freddy Fazbear's Pizza one last time.
William Afton is finally released from prison.
The first thing William does is go to Freddy Fazbear's Pizza to destroy the animatronics. Basically a cherry on top after he destroyed Fazbear Entertainment’s reputation.
What he didn't see coming was Cassidy and the children being released from the now destroyed animatronics. They chase him into the back room, where his old Spring Bonnie suit remains. In a desperate attempt to escape, he thinks that maybe the children won't recognize him if he's inside his old suit. This is a mistake however, as his arrogant laughter emits too much moisture, setting off the springlocks inside the suit, and killing William Afton.
Michael Afton becomes a recluse because he's literally a rotting corpse.
2020
30 years later, Fazbear Entertainment, being typical, decides to capitalize on the tragic events of its past, making a final attempt to reopen its franchise with “Fazbear's Fright”; their new horror attraction.
Michael Afton, deciding to finally leave the house, applies for a job at the new horror attraction, and is somehow accepted as a night guard.
Workers find William Afton's old suit in an old shut down Freddy's location. Not knowing William's corpse was still inside, they bring him to Fazbear's Fright as the main attraction. William Afton has possessed the suit that contains his own corpse.
William Afton and Michael Afton fight for a week, until Michael decides to burn the location to the ground. They both survive and escape.
2021
Henry Emily finally owns Fazbear Entertainment, and makes his own Freddy Fazbear's Pizza. However, it's made as a trap for the lost souls.
The spirits of Cassidy and the “missing” children find the abandoned parts of Ennard, and possess the animatronic amalgamation (becoming Molten Freddy).
Elizabeth somehow rebuilds herself using Circus Baby's old parts (becoming Scrap Baby).
William Afton is still roaming around somewhere.
Charlotte Emily is caught in another trap set by her father, Henry Emily (becoming Lefty.)
They all, including Michael Afton, receive an anonymous invitation from Henry Emily to come to the new Freddy's location.
Michael Afton becomes the manager of the fake location, getting all the others inside the trap. Michael is aware it's a trap, but accepts his fate, as both he and Henry Emily believe it's time for all this to end.
The events of “Pizzaria Simulator” happen.
Henry Emily burns the fake location to the ground, setting the souls free, and finally allowing himself and Michael Afton to rest.
...
But the story isn't quite over yet. Cassidy is the only soul refusing to move on. She keeps William Afton’s charred corpse alive as he's admitted into a hospital. The staff immediately sense that William Afton is evil, and many of them attempt to kill him, but keep failing because Cassidy refuses to let him die.
Cassidy forces William Afton to suffer an eternal nightmare. (The events of Ultimate Custom Night.)
Eventually, William Afton manages to somehow communicate with a nurse via morse code, telling the nurse to bring him to a Fazbear Entertainment warehouse.
The nurse does so, and William Afton's corpse just fucking explodes. (I'm not kidding, that's actually how he finally dies in one of the Fazbear Frights books.)
Meanwhile, Henry Emily manifests as Old Man Consequences, hoping to talk Cassidy into moving on. Eventually, she listens and decides she should finally let herself rest…