Slate has a short article on what happens to cartoon characters when the actor who provides its voice dies. The recent passing of what some wags have called the "Pooh trifecta" -- John (Piglet) Fiedler, Paul (Tigger) Winchell, and Howard (Gopher) Morris -- made it a timely subject, if a bit morbid.
Its morbidity quotient is increased by the anecdote about Disney Studios being deluged by resumes whenever one of its voice actors passes away. Actors have to seize opportunities as they arise if they want to keep working, and it was probably their agents (who everyone knows are heartless) who licked the envelopes anyway, but it's a side of show business most people probably don't want to see.
The article did, correctly, point out that Winchell and Morris haven't done those voices in a while, having been replaced by soundalikes some years back. (Morris was a very busy man, and Winchell's voice, Disney management felt, had become too raspy to sound like himself.) Rather conspicuously, since they illustrated the article with a shot of the Pooh characters, the author didn't mention that Winnie the Pooh himself has been voice by a soundalike since the late Sterling Holloway's retirement in the 1970s. (I know, it's hard to think of someone who's been doing the work for twenty-five years as "the new guy", but he's still "doing" Sterling Holloway.)
A mention of Jim Henson wouldn't have gone amiss here, although puppets and cartoons aren't quite the same thing. The Muppeteers had retired Rowlf (the piano-playing dog) as a speaking part in Henson's memory, although his face still pops up from time to time. (Surely you didn't expect them to retire Kermit the Frog.) Unfortunately, they've reversed themselves on this, and Rowlf has started talking again.