Mark Ruffalo was originally cast in Signs (2002), but left the film prior to shooting due to the discovery of a brain tumor. Ruffalo dreamt he contracted the tumor during shooting of Signs, which provoked him to visit a doctor. The tumor was benign, but Ruffalo took nearly a year to recover and lost hearing in his left ear. Production of Signs moved forward, and Joaquin Phoenix took Ruffalo's spot.
Mark Ruffalo and Joaquin Phoenix shared a house during filming.
The house number of the Learners is 187, which is the police code for murder.
Based on the novel by John Burnham Schwartz of the same name. Schwartz and the director Terry George wrote the screenplay for the film.
The gas station where the family stops, is actually the Olde Blue Bird Inn in Easton, Connecticut.