According to the screenwriters on Selling Your Screenplay podcast #81, the only reason the film was greenlit was due to a pending Actor strike in Sept 2000, so it was written in 10 days in May, filmed in June and wrapped in August- unheard of for a major studio film.
In his 2019 autobiography "Baby Don't Hurt Me", Chris Kattan noted that Paul Thomas Anderson (writer-director of Boogie Nights and Magnolia) and Richard LaGravenese (screenwriter of The Fisher King) each assisted with rewriting the script for Corky Romano, and they received no official credit. SNL writers Matt Piedmont and Scott Wainio also contributed to the rewrites.
Originally advertised as Corky Romano: 'Special' Agent, the movie was released as simply Corky Romano. The term 'special' with the marks around it was thought be making fun of a character's mental disability.
According to Chris Kattan , he originally portrayed Corky Romano more realistic and less like a caricature. But after Disney executive Peter Schneider fell asleep while watching the first rough ensemble of a footage shot during the first three weeks of production, producer Robert Simonds ordered all the footage that had been assembled at that time to be re-shot. Because of the tight budget, these re-shoots could not be done separately but had to be incorporated into the rest of the shoot, and Simonds insisted that Kattan play the lead in a much more cartoony way, smiling constantly.