Ronald McDonald has been on the scene since 1963, and after 50 years, it would be an ideal time for him to retire considering the childhood obesity rates, and of course, I have been a fan of the "Retire Ronald" campaign from Corporate Accountability International (formerly INFACT), a membership organization which has successfully challenged irresponsible and dangerous corporate actions around the world since the late-70s, such as the marketing of infant formula in developing countries which has put babies' lives in danger.
A number of other fast food mascots have been retired, with the most recent being Colonel Sanders being progressively retired by not using his figure at new KFC outlets.