Katie

Katie tells Micah a presence has followed her since she was small. He sets a camera up in the bedroom. She starts leaving bed in a trance and, by the end, acts possessed. On Night 21, Katie returns to the bedroom with blood on her shirt and lunges at the camera.

Katie's sister, Kristi, is possessed. Daniel and Martine pass the demon to Katie by burning a photo of her. Weeks later, the possessed Katie enters the Reys' house, kills Daniel and Kristi and takes baby Hunter.

On the 1988 tapes, young Katie is attacked by a dark figure and flung across the room. At Grandma Lois's house, she is beside her grandmother when Dennis is killed, and Lois tells both girls to get ready.

In 2011, Katie resurfaces in Nevada as Robbie's mother, living next to the Nelsons. She tells Wyatt he was adopted and his other family wants him back. Katie snaps Ben's neck and is the one who appears behind Alex at the end.

Hector goes through a door and lands on the day of the first film. Katie takes him for an intruder, screams for Micah and then stabs him to death, showing how the first film ends.

In 2013, adult Katie, posing as a real estate agent, sold the house to the Fleeges, and on the 1988 and 1992 tapes she and Kristi train their powers with a mysterious man.

In the first film the actors used their own first names, Katie Featherston and Micah Sloat, and improvised the dialogue. According to Wikipedia, Featherston returned to the role in the second and fourth films.