Dan's passport photo where he is a very young child is clearly more than 5 years old, yet youth passports in Australia have to be replaced every 5 years.
The postcards Dan's mother gave him have two 50 cent stamps on them, yet more than $1 postage is needed to send postcards overseas (to Switzerland); the correct price is $1.20.
Dan's English assignment is an analysis of the symbolism behind the fish-tank scene from Romeo + Juliet (1996). However, when we see him typing the assignment on his computer, the text onscreen has little to do with the scene in question, and appears to be a review of the film's DVD release - the text is, in fact, taken from Urban Cinefile's review of the DVD.
When Dan is searching on the Internet for a Pesto Recipe, the address on the browser reads "file:url", therefore he is accessing a webpage that is not actually on the Internet.
When Dan and Imogen are looking for a room in which to make out, they hear a couple having sex in one of the bedrooms. The sound effects that are heard are exactly the same as the ones made by Naomi and Jason earlier in the film.
In the subtitles, Naomi's spoken phrase "Give me some kind of dialogue!" (when she's arguing with Jason) is rendered as "You think that's gonna solve it all?"
When Jacq and Dan are driving from the airport they cross the Story Bridge. The direction signs above them show they are traveling north, however the airport is ON the north side of the river, so southbound would make more sense. In any case, their destination appears to be around Bardon, which is on the same side of the river as the airport.
Following the Story Bridge observation, we see Dan and Naomi visiting the Rosalie shopping center (near Bardon), but we see Dan boarding the ferry at Mowbray Park, which is a long way from those suburbs. In fact, no ferries service his school, and he would have a short bus ride from Bardon.
English assignments in Brisbane's Greater Public Schools (Brisbane Boy's College, which Dan is a student of, is one of these) at high school level are usually submitted around halfway during a ten-week term, or near the end of it, and usually consist of 1000 or more words. However, Dan submits a 2000-word essay within a week. Additionally, a single lesson (or even a double-period lesson) would not be sufficient for students to be familiar with "Romeo and Juliet" enough to begin their essay, but Mr. Wilkes seems to believe that it does.