Alternative Character Interpretation: The mother. Is she a good mother who wants the best for her children, including introducing them to their lovely grandparents whom she has a bad history with? Or is she neglectful and selfish, sending her kids away so she can have a cruise and brushing off their concerns about their grandparents so she can continue to enjoy herself? The fact that she hated her parents for fifteen years because they didn't approve of her substitute teacher dating her implies she's at least not the most reasonable person, but it is in her favor that she tries to call the police and save her kids the moment it becomes apparent that they're in danger in the actual film.
How much of Nana's interactions with the children was an act? Pop Pop seems to be the brains behind what is going on. She does have her creepy moments but it isn't until the end of the film where she physically attacks one of the children, and by then it seems like she has gone completely off the deep end. For all we know, Pop Pop killed the grandparents by himself and just brought poor Nana along for the ride.
Angst? What Angst?: The end of the movie has Becca and Tyler seeming to suffer no ill psychological effects of being held prisoner by two mentally ill people, learning their grandparents and one other woman they met had been murdered, or having to kill two dangerous people themselves. If anything, they seem better than ever. Becca actually comes across as healthier, and the credits even play over Tyler rapping about their entire experience.
Base-Breaking Character: Tyler. People either find him and his rapping unbearably annoying and unfunny or think he's hilarious and even endearing at times.
Crosses the Line Twice: The scene where Pop Pop smears his soiled diaper in Tyler's face. Especially considering the PG-13 rating.
The major dramatic moment of the climax, which has been carefully set up throughout the whole film, is an adult diaper getting rubbed in a kid's face.
Tyler's penchant for rapping, while intentionally awkward at times, can make one cringe due to the amount of it shown in the film. Including the end-credits where he raps about their whole experience with no trauma whatsoever, describing what it was like to have an adult diaper shoved in his face, etc. In the latter case, he sort of implies it's a coping mechanism.
If you've seen the trailers for the movie, you may remember Nana saying the line, "Can you get inside the oven to clean it?", and you were probably conflicted over whether or not that was supposed to be scary.
Squick: Nana projectile vomiting at night, coupled with the "lovely" shot of her in her undergarments the next night.
Pop Pop keeping all his dirty diapers in the shed out back. Nana's explanation seems reasonable, but considering the mental unstability of both of them, he could just be doing it for no real reason at all.
Made even worse during the climax of the film, when germaphobe Tyler gets a dirty diaper shoved into his face by Pop Pop.
Unintentionally Unsympathetic: Loretta can come across as not very sympathetic, considering the rift between her and her parents (which started when she struck her mother) was initially caused by the fact they didn't like her boyfriend... who was also her substitute teacher. A man who wound up abandoning them eventually anyway.
What an Idiot!: Stacey, you know these people are the escaped mental patients. You know that the people living at the house you're visiting haven't been seen for days. You're actively confronting said mental patients. Why are you going to follow them behind the house instead of getting help?