PIE Headquarters is the base of operations of Paranormal Investigators Extraordinaire and its two best-known operatives, Johnny Ghost and Johnny Toast. Its first appearance (and its first proper mention) is in the RUNNING FROM THE POLICE!! Gmod Apartment Raid Map (Garry's Mod) video, in which Ghost, Toast, and a number of other PIE members fend off a Metro cop raid after Toast's prison break. It has a machine that scans for paranormal activity.
It marked its first appearance in the RUNNING FROM THE POLICE! Video, although it has been mentioned in earlier videos, albeit briefly. The apartment was subject to a raid by the police after Johnny Toast broke out of jail. The apartment itself is part of a large block of flats, one of which is co-owned by Papa Acachalla. Billy and Gertrude were present during the raid, but in a different part of the building, during one of Johnny Ghost's time warps. They were not aware of the presence of PIE as they were in another part of the building and attributed the police raid to Papa Acachalla's gang involvement. (Gmod APARTMENT RAID Survival Map! Mod (Garry's Mod)) They later stormed the apartment under cover of dark using night-vision and cleared the police presence. (Gmod Splinter Cell NIGHT VISION Goggles Mod! (Garry's Mod)).
PIE HQ also made a brief appearance in PLAYABLE ANIMATRONICS 2! - Gmod Five Nights At Freddy's 2 Pill Pack (Garry's Mod), in which Johnny Ghost fell asleep whilst looking into a case for a man named Bobby, who claimed his mother-in-law was a poltergeist. In his dream he imagined the "Johnny Ghost and Johnny Toast Paranormal Investigation Headquarters" as a massive multi-complex building with multiple floors, which he used to dispatch various FNAF characters - Mangle was sent to the modern art iron monster, Bonnie to the firing range, Chica to the recently-opened bakery department, and Balloon Boy to space. Toast also dressed up as Marionette as a prank and was sent to the Priest to be exorcised as it appeared he was haunted again. When he followed Balloon Boy into the Nothing, he realized he had fallen asleep and woke up to find Freddy Fazbear applying for a job, to which Ghost replied that he had worked at PIE since 1987. Freddy went into the wrong room, however (which was revealed to be Toast's changing room) and died.
In one of the world's seen during Ghost's tenure in the Dream Zone, their apartment was mentioned as being raided during the squirrel invasion. This was also revealed to be a dream when Ghost finally found the door out.
During the Hurricane series, the team relocated to a deserted PIE base in Kansas. However, they left again a few months later after all the tornadoes in the world disappeared.
In SCARY BABY MOD! - Gmod FNAF Sister Location Mod (Garry's Mod), Ghost, Toast and Bad Texture Bronson are seen in a PIE HQ in "downtown West Switzerland" during a zombie outbreak. According to Ghost, they bought the building "for like, a thousand bucks, which is like, super cheap when you think about it 'cause it's like a whole building". The building in question was heavily run-down and in need of restoration, to which Ghost described as "a work in progress". The building is also supposedly haunted by a baby-like figure.