No re-shoots were required, a rarity for a movie as big as this.
The car used by Will Smith's character is a concept car called Audi RSQ, which was designed exclusively for the film and includes special features suggested by director Alex Proyas.
The corporation in the movie is called "US Robotics". A company under that name exists in the real world too (presently "USR"). Both got the name from Isaac Asimov's works and its fictional company "US Robotics and mechanical men".
For the character of Sonny the accused robot, the effects team used the same process that was used to create Gollum in the Lord of the Rings trilogy, with Alan Tudyk providing the body movements and voice for Sonny.
Director Alex Proyas had a difficult time with 20th Century Fox studio head Tom Rothman, who was threatening to remove the film's ending and replace it with "more jokes" just days before the film's premiere. Proyas intended to write a book about his experience making the film, which he describes as trying to run a marathon with the studio constantly throwing chairs in his path, but friends warned him that he'd never work in this town again. Even without the tell-all, I, Robot was his last studio film.