The restaurant where Matthew overhears Lisa talking on the telephone is called "Bellucci". Monica Bellucci was the female lead in the French original The Apartment (1996), of which this film is a remake.
Josh Hartnett signed on after Paul Walker was forced to drop out due to complications with the filming of 2 Fast 2 Furious (2003).
Both Diane Kruger and Rose Byrne plays in central female roles in this movie as well as in Troy, both released in 2004, just 4 months apart.
The newspaper article written about Daniel's wife's death is actually just one short paragraph, repeated over and over and over again.
The play Alex is in is Shakespeare's "Twelfth Night."