For Disney, he portrayed Roger in The Barefoot Executive (his film debut). He also appeared in some television specials in the 1980s, including guest-starring in Donald Duck's 50th Birthday in 1984, playing Dudley Goode in Mickey's 60th Birthday, and hosting Disney's Living Seas in 1986. Additionally, he played Vaughan Cunningham in Sling Blade and Bob Chipeska in Bad Santa (the latter of which was dedicated to him). He also voiced Great Uncle Stew in Stanley's Dinosaur Round-Up. The latter was his final film and it was dedicated to him.
On September 11, 2003, Ritter felt ill while rehearsing scenes for the second season of 8 Simple Rules. He was sweating profusely and vomiting and complained of having chest pains and was rushed to the Providence Saint Joseph Medical Center (the same hospital he was born in). Doctors believed Ritter suffered a heart attack, but it turned out to be an aortic dissection and he died that evening during the surgery. He was 54 years old, 6 days before his 55th birthday.
- Shortly after his death, Amy Yasbeck founded the John Ritter Foundation for Aortic Health in honor of him and to give other people life-saving reminders to recognize, treat, and prevent thoracic aortic dissection.