David Gerrold, the author of the book, adopted a son as an openly-gay man. In his novella, the sexuality of the protagonist is not disclosed, but in his novel, he is identified as gay. In the film adaptation, the protagonist is straight (with a female love interest), causing some criticism from members of the gay community.
Director Jerry Zucker was brought in to shoot new footage, according to Patrick Goldstein in the Los Angeles Times on 10 August 2007.
When David and Dennis were in the grocery store Dennis stopped and stood next to a stack of Mars bars.
John Cusack would once again team with Amanda Peet and Oliver Platt in the disaster movie 2012 (2009).
An early novel by screenwriter David Gerrold was called "When H.A.R.L.I.E. was One." Amanda Peet plays a character named Harlee.