Do you remember Clara Peller and her wildly popular Wendy's ads? According to Wikipedia, she was 81 when she took the commercial gig. It all began in 1984, as she continually demanded, "Wherrrre's the beef?!?" Her insolent query became an instant catch phrase, and her relentless search for the beef became legendary.
Despite the ad campaign's huge popularity, the Wendy's ride came to a halt for Clara in 1985, when the famed hamburger joint fired her for doing a Prego sauce ad in which she declared that she had "found the beef." (Phew! Mystery solved. No more searching for the beef...)
Besides her commercials, Ms Peller had appearances in a couple of movies, on Saturday Night Live, and even at WWF's WrestleMania 2 pay-per-view event.