Brianna Gardner, who played Cadence the little burn victim girl, is the daughter of the movie's makeup artist Tony Gardner. She can be seen with him in the movie's closing credits.
The large conference table used when Hal gives his presentation is rumoured to cost over $1 million dollars. It belongs to the company who let the crew use their offices for filming.
The Farrelly brothers called the main female character Rosemary just so they could use the Edison Lighthouse song "Love Grows (Where My Rosemary Goes)" during the end credits (DVD commentary).
Most of this movie was filmed in Charlotte, NC. The shots of Freedom Park where you see the water and small bridge; "Arboretum" is a shopping center / community, and the panoramic shots of downtown are all notable.
The film is dedicated to Charles Seabrook, who worked in the camera and electrics department for 'Shallow Hal', who died of a heart attack six months before the movie was released.