Defined as characters used as representatives for products long after the cartoon they were in has been blown up.
This is inspired by the hot chocolate we have at work, which is Kayo brand, Kayo being a character from Moon Mullins. Maybe some paper somewhere is still running that strip (I’m too lazy to look) but it was long in the tooth when I read it in the Daily News 40 years ago.
Another example is Flintstones. We might even consider Mickey Mouse one, since new Mickey cartoons are few and far between.