For the first Cars, Pixar did a scene in which Sally and Lightning McQueen go on a date at the theater to watch a film starring Finn McMissile, but it did not make it to the final movie.
In the post credits scene, when Mack comments on one of the actors from A Bug's Life, he says that they are just using the same guy over and over again. Ironically, Mack is voiced by the same actor that plays Hamm in Toy Car Story, the Abominable Snowplow in Monster Trucks, Inc., & the P.T. Flea Car in A Bug's Life.