Continuity mistake: In the treehouse, the contraption Henry built releases icing in a pile onto the top of the cupcake (or brownie) Peter is holding. When Peter moves the cupcake to his mouth, the icing is evenly spread in the middle. (00:07:04)
The Book of Henry (2017)
Ending / spoiler
Directed by: Colin Trevorrow
Starring: Naomi Watts, Jacob Tremblay, Jaeden Martell
Glenn commits suicide (shoots himself at home during the talent show) and a judge orders that Susan becomes Christina's permanent legal guardian. Susan reads her published children's book to Peter and Christina, who are temporarily sharing the bedroom (until another room is painted). It is bedtime, so as Susan is leaving the bedroom, she asks "On or off?" (lights), to which both kids say "on." Then, "Open or closed?" (door), and the kids both say "closed." [Henry and Peter used to give opposite answers when asked these questions].
More mistakes in The Book of Henry
Susan Carpenter: OK... Fuck it.
Peter Carpenter: You're not supposed to swear in front of me.
Trivia: Although relatively rare and quickly dwindling, there are still some (100,000?) functional payphones (coin-operated or credit card) in the US, including in New York. It is doubtful there would be one outside of Henry's elementary school, but pay phones are typically near public buildings.