Continuity mistake: At the beach when Zach and Laney are leaving it is sunset. In the next scene at Laney's house it is mid afternoon at the latest. It has to be the same day because they attend a party that is mentioned as "tonight".
Other mistake: When Laney goes to the beach she's carrying a huge book. When they leave the beach, there's no book.
Answer: Zach's sister is Anna Paquin. She's been in tons of stuff like Almost Famous and she's the kid in The Piano, but she's mostly known as Rogue in the X-Men movies. The 'other one' is Clea DuVall who's been in 21 Grams and Girl, Interrupted. She was also the girl who disappears in a first season episode of Buffy. Stick the names into the IMDB to find out more.
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