Continuity mistake: While being sorted into houses, Harry looks up at the Sorting Stool, and there are only three people left to be sorted. Professor McGonagall then calls out the names of four more kids.
Suggested correction: This is incorrect. After Harry is selected for Gryffindor, McGonagall calls Lisa Turpin, Ron Weasley, and Blaise Zabini, three students.
This is actually a difference between the British and American releases. In the British (Philosopher's Stone), Lisa, Ron, and Blaise are called, making three students. But in the American (Sorcerer's Stone), Dean Thomas is also called, making four students; however, the book still states only three students remain.
Interesting fact; I didn't know that. I guess not calling Dean Thomas in the British release could count as another mistake.