Accidental Aesop: For Paranormal Activity 2: Never foist your problems on your in-laws.
Alternative Character Interpretation: The demon in the first one. Despite what is revealed about it in the later installments, more than one watcher thought to themselves that they would probably kill Micah too, if they were demons and he stayed in the place they lived all day and yelled at them for moving stuff or doing anything aside from sitting quietly and never moving or making any noise.
Complete Monster: SweetGrandma Lois is revealed as the worst the series has to offer in the third entry in the series. All of the horror stemming from the demon plaguing the family can be traced back to her. It is revealed that Lois is a witch and the head of a coven that bargained with the invisible demon, in return for personal gain, to surrender the first male member of the family to the demon. To that end, Lois allows her daughter, her daughter's boyfriend and two young daughters into her home along with the demon. Lois orchestrates the death of her own daughter and watches her boyfriend's brutal death when the man tries to rescue the little girls. The film ends with Lois about to conduct a ceremony with the little girls and the demon, fully aware that eventually her great-grandson will be taken by the demon and her granddaughters' lives ruined or ended, all because of Loisís personal greed.
Darkness-Induced Audience Apathy: It doesn't seem to matter how much you grow to love the characters, They all die in the end because the cult is a God-Mode Sue that's nearly impossible to stop. After five movies with this pattern, are you hoping for an ending where the good guys finally come out on top? Nope, that doesn't happen either.
Ensemble Darkhorse: Dennis of 3, probably for being more competent and likable than Micah and Dan. Also, Ben from PA4.
Arturo from The Marked Ones is getting some love from fans for using a shotgun to kill some witches.
On a similar note, in 3, when Katie is beating the hell out of a piñata at her birthday party, Dennis jokingly comments that "(Katie's) a little monster".
Harsher in Hindsight: Katie's shrieks of terror at the end of the first film are frightening enough. Then came the ending of The Marked Ones which reveals that Katie wasn't in control of herself while screaming for Micah, as it originally seemed - it was the demon using Katie to lure Micah downstairs.
The death of Doug (Alex's father) in 4 becomes somewhat harder to watch with the knowledge that his actor, Stephen Dunham, died shortly before the film was released.
Hype Backlash: Much like The Blair Witch Project before it, getting so many reviews dubbing it one of the scariest movies of all time ensures that some people will watch it and end up unimpressed.
It's the Same, Now It Sucks: An already common criticism of Paranormal Activity 2 and the following sequels is that it too frequently uses familiar scenes from the first movie.
Jerkass Woobie: Micah; arguably Dan as well. Yes, they are unsympathetic for a lot of viewers, but eventually Micah all but abandons his Jerkass and It's All About Me attitude and shows that he really does care about Katie. In the case of Dan, while his act of transferring the demon to Katie is seen by some as a Moral Event Horizon, he does it out of his desperation to protect his wife and son. Unfortunately for him and his family, it doesn't work.
Narm: While the footage of Robbie climbing into bed with Alex is supposed to be creepy, many people found it more adorable.
Signature Scene: For the first film, either the foot drag scene or the ending.
For the third film, the scene where Toby uses a bedsheet to mess with the babysitter.
Surprisingly Improved Sequel: The Marked Ones seems to be less divisive than 2, 3 and 4 with some fans and critics feeling it to be up to par with the first film and enjoying the expansion to the series' mythology.
Uncanny Valley: Those possessed by the demon tend to move slowly and stiffly.
The first time Katie shows up in Paranormal Activity 4, she's completely in her demon-controlled blank effect mode for just long enough before acting normal that it becomes this.
Visual Effects of Awesome: Toby's semi-corporeal form, a tall, vaguely-humanoid mass of smoke and tendrils, is suitably impressive and unsettling.
The Woobie: Ali in 2. First her parents don't believe her when scary things begin to happen, one day her stepmother wakes up acting like a cross between a wolf and a serial killer. Then, oh, things are looking up! No horror for three weeks! Until you come home to find your family brutally murdered and your baby brother missing.
Any heroic dog in a horror movie is almost contractually obligated to be the most sympathetic character in the movie. Hence, Abbey. But thankfully she lived. The same goes for Chavo from The Marked Ones. The poor little guy ends up getting tortured by his now possessed owner.
Dennis in the third film. He deeply loved his stepdaughters and wife and wanted to find out about the demon and save his family. Yet his wife dies in front of him and he is killed by his mother-in-law. All while trying to save his stepdaughters.
Kristi. The events of 2 and 3 would have been prevented had they just listened to her. Also, Dan (in the second) and Katie (in the third) are mean to her for little reason.
Katie. Imagine being haunted constantly by a demon and spending the rest of your life possessed by it, where you have killed several people including your own sister with no control. AT ALL.
Alex from 4. It wasn't her fault that she and her family adopted the one boy the demon was after.
Hector from The Marked Ones. He's forced to watch his best friend slowly become a monster in spite of his efforts to save him, and ends up getting killed by him after spending several minutes fleeing in sheer terror. Not only that, but he also discovered the corpse of his other friend Marisol.
Irma from The Marked Ones. She loves Jesse and risks her life to try and exorcise the demon from his body, only to have her possessed grandson push her down the stairs for her efforts, resulting in her hospitalisation.