"Toby" is the demonic entity from the Paranormal Activity movies, and the main antagonist of the series. This is not the creature's real name; it is the name Kristi Featherston (later Kristi Rey) gave to the demon in Paranormal Activity 3. Toby's true name has not been disclosed as of Paranormal Activity 3. The footage documented in the movies have so far implicated Toby in the deaths of (in order) Julie, Dennis, Micah Sloat, Daniel Rey, and Kristi Rey, as well as the kidnapping of Hunter Rey and the disappearence of he and Katie Featherston.
Toby's age and even gender are unknown, though in Paranormal Activity 3 Kristi refers to it as "he". His age is suggested when Kristi states Toby is "old like Grandma". As for sex, when Dennis was exploring Lois' house, he was stalked by a dark, female shadow, and during Kristi and Katie's second Bloody Mary game, a female-looking figure appeared in the mirror as they left. However, the shadow stalking Dennis bears a sharp resemblence to Lois. As for the female figure that appeared to Kristi and Katie, that has more to do with the Bloody Mary game itself. The entire purpose of the game is to summon the ghost of Queen Mary I, who was known as Bloody Mary because of the many 'heretics' she executed in the 1500s.
Toby appeared to one or more witches sometime in the 1930s and arranged a deal. Toby would grant wealth and supernatural power to any who asked for it in exchange for the life or soul of the next male to be born into that family line. Among those supernatural powers were inducing artificial amnesia and summoning Toby, as well as other demons. Over the next fifty years the family produced four different women but no men; Lois, her daughter Juli, and her own daughters Katie and Kristi. Toby spent this time silently haunting the family as he waited for his payment.
Sometime in 1988 Toby made himself known to the youngest daughter of Julie, Kristi. Julie's boyfriend Dennis, who was living with the family at the time, first recorded Toby accidently and unknowingly in September 1988, when Kristi was playing with it under a trampoline during her sister Katie's ninth birthday party. Toby took up residence inside a crawlspace in Kristi's and Katie's room and engaged in late-night games with Kristi. They would play hide and seek and climb on furniture. At one point Kristi jumped twelve feet from a ledge into the safety of Toby's waiting arms. During the day Kristi and Toby continued contact through tea parties and "the knocking game"; Kristi would knock three times on a closet door, and Toby would knock back from inside. The rest of the family assumed Toby was an imaginary friend Kristi had dreamed up; Dennis was amused by Kristi's knocking game and even offered Toby a pat on the shoulder while particpating in a tea party.
Kristi was not the only person Toby played with. Dennis first discovered Toby when an earthquake disrupted a sex tape he was making with Julie; the camera recorded Toby shaking a cloud of dust off himself. Toby once followed Julie downstairs as she had a midnight snack, but expressed displeasure with Julie saying, "God damn it!" to her garbage disposal and dropped a lamp on the floor. When the girls' baby sitter Lisa took a sheet from Toby's crawl space and pretended to be "the ghost", Toby snuck up on her while she was studying and dropped the sheet at her feet. When Lisa went to put the sheet back, Toby blew a puff of air in her face and scared her. Toby also appeared to Katie during a game of Bloody Mary, slamming a door when she and Kristie left for a swimming pool.
In Paranormal Activity 3, Toby at first maintained a friendly relationship with Kristi, but showed animosity for her family from the very start. While investigating the sounds of Toby's footsteps, Dennis follows Toby into its crawlspace. Toby was deeply offended and vented to Kristi about the incident, but Kristi stood up for Dennis, calling him "sweet". Toby later spooked Dennis through loud noises and by slamming window shutters behind him. Dennis and later Julie also provoked Toby by interrogating Kristi about her games and conversations with it, things Toby had told Kristi to keep secret. When Kristi and Katie were having a backyard campout, Toby became frustrated when it was unable to find Kristi and took it out on Dennis and Julie, locking them inside the house and separating them. He lured Dennis into the girls' room to get him out of the way while he punished Julie, but Dennis retrieved Julie before Toby could get her alone in their bathroom. Toby let the matter drop after Julie brought the girls back into the house.
Katie accidentally-on-purpose provoked Toby multiple times through picking on Kristi, summoning him twice through Bloody Mary games, and also by taunting him before entering his crawlspace. Toby locked her inside of it twice, only letting her out after Julie and later Kristi interfered. When Katie was chasing Kristi up stairs in pursuit of a doll, Toby blocked her way and yanked her up off the floor by her hair. Katie enraged Toby to the point he stayed permanently angry with her, even over fifteen years later.
On the night of September 22, 1988, Toby possessed Kristi and walked her into Dennis and Julie's room, where Kristi stood and stared at the couple for over an hour. Judging by Kristi's later reaction and footage from Paranormal Activity and Paranormal Activity 2, Toby may have tried to use Kristi to kill Dennis, Julie, and Katie. Kristi was deeply disturbed by this, in addition to a request Toby made later that night. Toby was growing impatient and wanted to mate with Kristi to father her child in hopes of producing the male heir he had been promised. Kristi refused to give in to his demands and told Toby to stop talking to her. In a rage, Toby gave Kristi a high fever and brutally attacked Katie and Dennis' assistant Randy the following day. Later that night the furious demon trashed the girls' room and dragged Katie into his crawlspace, holding her hostage until Kristi agreed to do as he asked. Toby told her to go to Lois' house to prepare for a binding ritual. Julie at first denied Kristi's plea and Toby's very existence. In response, Toby dropped the kitchen furniture on her.
When the family arrived at Lois' house, Kristi and Toby played in the yard while Julie told Lois about everything that was happening. That night Lois summoned the witch coven and pulled Kristi and even Katie out of their bed to prepare for the ritual. Julie and Dennis were awoken by the sounds of approaching vehicles and Julie went to investigate. She witnessed the coven in the garage and was murdered, presumably by Toby. Dennis followed her and discovered Julie's death when Toby threw her body down a flight of stairs on top of him. When Dennis found Kristi cowering in a nearby room. Toby attacked the both of them and chased them into a closet. Unable to get to them, Toby possessed Katie and lured Dennis over to him by making her cry over Julie's fallen body. When Dennis got close enough Toby had Katie break both his legs. Toby later snapped Dennis' spine, folding him over backwards and killing him. Lois then took Kristi and Katie upstairs to finish the ritual. Toby followed after spitefully stomping on Dennis' camera.
(edits for PA2 and PA1 forthcoming)