Based on a true story, though some elements have been changed from the book. For instance, Gardner's internship was not unpaid; he received a small stipend. He and his child's mother were never married.
Dan Castellaneta, who voices Homer Simpson on The Simpsons (1989), co-stars in the film as one of Gardner's superiors and requests a donut from Gardener. This is a nod to Casellaneta's animated counterpart who shares a similar taste for donuts.
Throughout the film, period advertisements for Pacific Southwest Airlines can be seen in numerous places (taxis, buses, BART stations). PSA was a very popular low-fare airline in California during the period in which this film is set.
Young Christopher often plays with, and would later accidentally leave behind, a Captain America doll. A legendary Marvel comics character who would later have his own movie franchise five years after this film was released.
The title "The Pursuit of Happyness" is misspelled, as the correct spelling is "happiness." "Happyness" is not found in the dictionary and is not a word in the English language. It was spelled that way on purpose, because it appears written the same way on the outer wall of Christopher's (Jaden Smith's) daycare center.