- Beam Me Up, Scotty!: A running gag is Will misattributing the saying "No man is an Island" to Jon Bon Jovi rather than John Donne.
- Creator In-Joke: In Ali's room in the film, there's a poster for Arsenal FC. Nick Hornby, the author of the book, is a huge Arsenal supporter.
- The Danza: Rachel Weisz as Rachel.
- Fake Brit: Toni Collette is Australian playing an English woman.
- Star-Making Role: This was Nicholas Hoult's first major role that would lead him to Skins and the X-Men films.
- Throw It In!: The shot of Will reflected in the mirror looking depressed was taken while Hugh Grant was on a break. The filmmakers saw this and shot it from behind without him knowing.
- What Could Have Been:
- Brad Pitt of all people was offered the lead role. He turned it down, not thinking he'd be able to play someone who would have to pretend to be a single father to meet women. Colin Firth was interested and even contacted Nick Hornby, but it had already been optioned as a film by the time Firth called. George Clooney, Russell Crowe and Ewan McGregor were also considered.
- Emma Thompson was offered a role.
Trivia / About a Boy