The running gag of Ratzenberger portraying at least one character in every Pixar movie is referenced during the end credits of Cars; when Mack watches the Cars-parodies of previous Pixar films and he thinks that whoever did the voice of Hamm, Yeti, and P.T. Flea (all in car form) were great actors until he realized it was the same voice actor in all those films and asks, "What kind of a cut-rate production is this?".
P.T. Flea from A Bug's Life is Ratzenberger's personal favorite character of his Pixar roles.