A Poltergeist was a spirit, such as a ghost or apparition, that could manifest visually and audibly, influence minds and alter reality.
- "I think we're dealing with a kind of Poltergeist, a cluster of them in fact, born out of intense adolescent emotion and sexual energy."
- ―Rupert Giles[src]
The ghosts of James Stanley and Grace Newman manifested at the time of the Sadie Hawkins dance at Sunnydale High in 1998. The two previously had a student-teacher affair over forty years ago, but it resulted badly when James shot Grace dead after she ended the relationship, and then killed himself.
James' spirit, seeking forgiveness, began possessing students and faculty along with Grace. Hoping to relive the moment, the possession victims however reenacted the scene to the exact moments, resulting in the death of one teacher and the near death of two students and janitor which where saved when Buffy Summers and Rupert Giles intervened, cutting off the possession and making the mystically created gun disappear. Aside from that, James also began wrecking havoc, forcing the school to be temporarily shut down. The Scooby Gang attempted to bind James' spirit by creating a Magnus Tripod at the school, however, James summoned a swarm of hornets, forcing them to evacuate and preventing them from returning. James, having related to Buffy, drew her to the school safely and whilst Angel came by chance, reenacted the event once more with Grace, only for it to end happily as Angel, being a vampire, resisted the bullet wound and allowed Grace to reunite with James so that their spirits could move on.
The original owner, Maude Pearson, who killed her own son, Dennis before dying of heart attack, haunted the Pearson Arms apartment decades after her death. In that time, Maude's ghost killed three female occupants because she was under the impression they were involved with Dennis. When Cordelia Chase bought the apartment in 1999, Maude continued her streak and began constantly and violently attacking her. Angel and Doyle then attempted to exorcise her but this was interrupted when a loan shark's henchmen came to kill them. Cordelia, having had enough of Maude's torment, stood up up to her by reliving her days as "the nastiest girl in Sunnydale history". With that, Dennis was able to possess her so that he could reveal his body to his mother, sending her away. Even with Maude gone, Dennis still resided at her apartment as Cordelia's benevolent roommate.
- "So, with Buffy and Riley having, you know, acts of nakedness 'round the clock lately... Maybe they set something free. Like a big bursting poltergasm."
- ―Xander Harris[src]
In 2000, a poltergeist manifested at Lowell House as a result of the severe abuse, and repression of a group of traumatized teenage orphans at the hands of Genevieve Holt. These were not the disembodied spirits of deceased people, but rather spiritual manifestations of intense, raw emotions and energy of living people.
The teens' intense emotions, and sexual energy remained within the house and manifested because of the sexual relationship of Buffy Summers and Riley Finn, whose constant sexual activity acted as an energy source for the "poltergasm".
The poltergeist not only drew energy from Buffy and Riley, but also influenced them to continue engaging in sexual activity, forcing them to give them a constant source of energy until it runs out, which would result in their deaths. It was the efforts of Xander Harris and Anya Jenkins that permanently stopped the poltergeists when they simply walked into Riley's room and interrupting his being intimate with Buffy.
Powers and Abilities
Poltergeists have been shown to possess an array of powers. Most prominent power was the ability to move objects and people. Other powers, as shown by James Stanley and the Lowell House children, can alter reality as James was able to summon a large number of snakes out of nowhere, create an arm that attacked Xander Harris from his locker, and cause the floor under Willow Rosenberg to sink like quick sand. Maude was also able to imitate Angel's voice perfectly to trick Cordelia.
The Lowell House ghosts were able to affect the behavior of the party goers that reflect their sexual repression such as making Willow and Tara separate in disgust of each other when sitting close, making a "spin the bottle" game participant cut her hair in guilt, possess humans like Julie and Graham Miller and causing other strange occurrences like to provocate a cold climat in the room, the fire of the fireplace throwing itself on a student, the walls impregnated of carnal energy provoking orgasm to those who touches it, a bottle which turns by telekinesis to the point to explode, manipulated strips to attach Spike to a chair, a violent ejection on Xander when he tries to return inside, and a massive growth of vines and a local earthquake at the house as well as forcing Xander into a filled bathtub, drowning him like how the orphans were "baptized".
Dennis, James, and Grace also all showed the ability to possess the corporal bodies of both humans as well as a vampire in Grace's case. Though it appeared that this ability was limited in some way, as James and Grace only could possess people according to their past experience, which they could not properly resolve until they possessed Buffy and Angel, and Dennis apparently could not or would not possess Cordelia until she stood up to his mother. They also use intangibility like most ghosts do.