Ass Pull: The ending, where it turns out the characters are all aliens and Brent is a human whose parents made him invisible to hide him. But there are several problems with this twist: A. There's no foreshadowing that even remotely hints at this besides the characters' lack of any physical descriptions (which is not all that unusual) and a throwaway joke about the main character growing a tail, B. From what little description of the aliens we get, they aren't at all humanoid (apparently they have two heads and really long tentacle-like arms), yet their everyday life seems to work the same as if they were humans, C. There are a couple things from modern-day Earth mentioned (such as Corn Pops, and one character wears a New York Yankees jacket), which aliens would not reasonably have, D. The aliens have four arms and yet when Brent picked up Sammy, he didn't notice the difference at all, and E. When Roxanne is being attacked at the abandoned house, it's mentioned that her hair was spinning behind her head as she struggled, even though they supposedly didn't even know what hair was when they saw Brent visible. All in all, it seems likely the author just made up the Twist Ending right when he got to the end of the book and didn't think it out ahead of time.
The Scrappy: Roxanne is the most despised character in the book, and for very good reasons too. She is very abrasive and harsh towards Sammy most of the time, and despite being his friend, she is even willing to humiliate him in school by telling everyone about his imaginary friend without a single lick of remorse. While she has become nicer after learning Sammy was telling the truth, that does nothing to make up for the way she's treated Sammy beforehand.
Take That, Scrappy!: Roxanne being tortured by the "ghost" at the haunted house is very satisfying to read about after what she's done to Sammy prior to the arc.
Unintentionally Unsympathetic: Brett is meant to be an Anti-Villain and Tragic Monster, but is just such an asshole, (whose crimes include playing pranks and trashing Sammy's room to get him in trouble, as well as pretending to be a ghost and scaring the crap out of people just for funzies) that he just comes across as an outright villain instead.
