The original script (called The Yellow Car, about an electric car living in a gas-guzzling world), some of the original drawings and characters were produced in 1998 and the producers agreed that Cars could be the next movie after A Bug's Life and would be released in early 1999, particularly around June 4. However, the movie was eventually scrapped in favor of Toy Story 2. Later, production resumed with major script changes.

John Lasseter has said that the idea for Cars was born after he took a cross-country road trip with his wife and five sons in 2000. When he returned to the studio after vacation, he contacted Michael Wallis, a Route 66 historian. Wallis then led eleven Pixar animators in rented white Cadillacs on two different road trips across the route to research the film.^{[citation needed]}

In 2001, the movie's working title was Route 66 (after U.S. Route 66), but in 2002, the title was changed to prevent people from thinking it was related to the 1960 television show with the same name. In addition, Lightning McQueen's number was originally going to be 57 (Lasseter's birth year), but was changed to 95 (the year Toy Story was released).