Johnny Ghost/Timeline

Circa 1850's

 * Pee Wee Ghost, retroactively the third man to be labelled as the father of Johnny Ghost, and his brother Ernie Ghost (in actuality a future incarnation of Billy Acachalla) found the Steampunk PIE, a predecessor to the Paranormal Investigators Extraordinaire.

1986

 * Jordan's revision of Johnny Toast's age would place Ghost's date of birth around this year, since Ghost is two years younger than Toast. Shinogami and Chica both survived this event.
 * Police Officer Tommy Casket, the first man to be referred to as Ghost's father, is killed at the Olive Gardens restaurant in Little Butts, North Carolina, along with his partners Low Texture Johnson and Low Texture Bronson. Ghost stated in 2014 that as a result of his death, he and his mother were forced to live off of the wealth he had acquired during his lifetime.

1989

 * Ghost's original age places his date of birth around this year.

October 31st

 * Johnny Ghost remembers this date as the date his dog Quasar went missing and the date he saw the Mothman.

The Casket Years
At some time around the 1990's-2000's, Gregory Casket became possessed by the demonic presence of Jimmy Casket and committed an unknown number of murders across an unknown number of states for an unknown period of time. Casket is known to have a psychotic, childish personality, proclaims himself "the world's most renowned murderer" and is seemingly unnaturally strong, surviving many potentially or otherwise fatal injuries more times than any other serial killer (real or fictional) on record.

Eventually Casket was captured and placed in a high-security sanatorium where he was incarcerated until he was deemed safe to be released; by this time all traces of Gregory had seemingly vanished, along with Casket's, and in the intervening time, the boy had created a new persona based on his childhood friend Johnny and his own nickname; henceforth he went by the name of Johnny Ghost. What nobody realised, however, was that Casket merely lay dormant...

2000-2012

 * Johnny Ghost starts a paranormal investigation group in high school with Toast. When Toast leaves for summer camp, Ghost, then aged 16, replaces him first with new kid Dark Pit, and then with a malformed clone which accidentally gets sent back 20 years...
 * As the group evolved several additional members including Johnny Roast and Johnny Boast joined (though they were possibly from an earlier iteration of Ghost's group, such as junior school). As of 2016 most of these members are either deceased, retired, or missing in action.

2013

 * Johnny Ghost (later retconned into his unnamed father) investigates the haunted house of Kermit the Frog and is killed there.
 * Johnny Ghost's first real appearance is with his partner Toast hunting ghosts masquerading as props such as Aimee, Maxwell Acachalla, Cardboard Friend, Toilet Toucher, and even former partners Roast and Boast, and on occasion even turning into props themselves.

July 10th

 * During a call to Dakota to investigate a call whilst Toast is busy at the Rake's wedding, Ghost meets Cardboard Friend, who refers to him as "Gwegowy" and insists they are brothers, and also paints a picture of his father Tommy Casket on the wall. Cardboard Friend eventually annoyed him to the point that he briefly reverted to his Jimmy Casket persona and scared Cardboard Friend away, only to lose all memory of everything relating to the incident up to that moment.

June 24th - August 21st

 * Whilst investigating Swift Taylor's mansion, Ghost is killed and transformed into a puppet before floating into the sky and being sent into a dream-like state. This lasts for several months until he re-enters Earth's atmosphere and awakens after landing in Hell's Island, Germany. He is then returned to his human form by Toast and Barnacle, who knows his original identity.

March 9th - April 22nd

 * Having apparently finally discovered the existence of his insane serial killer alter ego Jimmy Casket, Johnny Ghost twice goes to Dipper Pines to remove Casket and accidentally splits himself and Casket into two bodies. Whether Gregory was also split is not known. Ghost (and, by extension, VenturianTale) is banned from ever returning to Gravity Falls.
 * During Toast's absence Ghost takes on Chris 'Colon' Ghosty as a new partner.

Undated events

 * At some point presumably long before 2013, Gregory Casket lived in an abandoned mansion in an unknown location with Cardboard Friend. When Cardboard friend makes Gregory think that he is dead, Gregory freaks out and runs away before seeing Cardboard Friend ascend (which some have speculated may have been Gregory's imagination, with in actuality Jimmy Casket stabbing and killing Cardboard Friend) before running away at spotting Gertrude approaching the house, which she had recently purchased.
 * During John and Jonathann's war in the desert a woman came back from the future to kill someone she referred to as "Jonathan Core" or something similar sounding, before John shot and killed her. (THE GALAXY IMPLODER!! Gmod EPIC Deathmatch! (Garry's Mod), October 15th 2015)