Actor-Shared Background: Diego Luna and Gael García Bernal were already best friends for years, and that was actually the main influence in Alfonso Cuarón giving the former the part; he had been reluctant to cast Diego, due to his Teen Idol status, but Gael convinced him that their friendship would result in a natural on-screen chemistry.
Dawson Casting: The boys are said to be teenagers. Gael Garcia Bernal was 23, while Diego Luna was 22. Of course, given the extensive sex scenes, casting older actors was necessary.
Enforced Method Acting: To prepare for the beach bar scene, the actors and crew were taken to the place two days before, got drunk and danced, improvising and saying what they wanted. They repeated the process the next night. And when the time came to shoot the scene, they relived what they had already done.
Harpo Does Something Funny: The actors were encouraged to improvise as filming went on, as there was a minimalist script that left room for expansion.
Playing Against Type: Directing example. Alfonso Cuaron had made stylised Hollywood dramas such as A Little Princess (1995) and the modernised Great Expectations, and wanted a change to work on a minimalist road movie with a lot of improvisation and shot in 90% natural light.
They initially couldn't get the rights to Frank Zappa's "Watermelon in the Easter Hay" because it was one of three songs he had requested never be played in any media except the album they appeared on. Gail Zappa, his widow, watched a cut of the film and gave her approval, deciding that her husband would be proud of it.
Isaac Sánchez was in the running for the role of Tenoch Iturbide, but since he was only 16 at the time, they went with the older Diego Luna out of thought for the sex scenes.
Other Trivia:
In the dance scene, near the end of the film (and in the movie poster), the position of the three characters is later referenced in another Alfonso Cuarón movie. Which one? HarryPotter◊.
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