I'm going to do a series of posts about this as it's the topic of a Masters thesis I'll be writing in the coming year. The first thing I want to talk about is that animators share characters in a way that live actors rarely do.
The first animated films by Blackton, Cohl and McCay were individual efforts. They did everything themselves, so there was no sharing of a performance. McCay hired an assistant, John Fitzsimmons, to help out on Gertie the Dinosaur, but Fitzsimmons just traced back all the backgrounds as no one had figured out how to use cels yet. So we can say that from a performance standpoint, McCay is Gertie.
Once studios came into being for the regular production of animated films, things changed. Dick Huemer talks about how work was split up on Mutt and Jeff cartoons in the teens in his 1969 interview with Joe Adamson.
"We were given a portion of the picture, over a very rough scenario. Very, very sketchy, no storyboards like we have today, nothing like that. The scenario would probably be on a single sheet of paper, without any models, sketches or anything. You made it up as you went along. You were given a part of the picture and you did what you wanted. If it was a picture about ice-skating, you took a scene of somebody on ice skates and you used your own gags and made it all up."This was hardly conducive to consistent performances. Later on, with model sheets and storyboards, scripts were better worked out. However, the splitting of a performance between animators continued to occur. The only exceptions were the rare cartoons animated by a single person (Plane Crazy by Iwerks, Rabbit Rampage by Washam, etc.) and the occasional cartoon where one animator got all of a character, such as Tytla animating the giant in The Brave Little Tailor or Preston Blair's animation of Red in Avery's MGM cartoons.
The norm is for multiple animators to handle a single character. Looking at Lonesome Ghosts, you have Ed Love, Izzie Klein, Milt Kahl, Marvin Woodward and Roy Williams all handling Mickey Mouse within the cartoon. Even in Disney features where we associate particular animators with specific characters, there are more hands involved. For instance, documents published by Mike Sporn show that in the opening scenes of Pinocchio, Ward Kimball, Ham Luske, Berny Wolfe and Don Towsley all animated Jiminy Cricket, where Kimball is usually credited with the character.
This remained the standard into the '90's, when the Disney studio was still casting animators by character. Glen Keane was the supervising animator on the Beast in Beauty and the Beast, but Aaron Blaise, Geefwee Boedoe, Brad Kuha, Tom Sito, and Anthony de Rosa all animated the character as well.
Live actors sometimes share a character. The most obvious example is when two actors play a character as a child and adult. Stunt doubles have been common in films at least since the 1920's. Now there are digital doubles as well, so there may be multiple people contributing to what we think of as a live action performance. However, the idea of doubling came about to prevent injuries to actors, not to compromise their performances.
Mike Barrier believes that having one animator handle a character is the only way to create a great animated performance. He discussed this on his website with contributions by myself and others starting on August 26th, 2005 and continuing at least until the following January. My point isn't that Barrier is wrong, but that this approach is often impractical given the limitations of a production schedule and budget. Furthermore, I believe that the nature of animated acting is far more fragmented than anyone realizes. The collaboration of several animators on a single character is only the tip of the iceberg when it comes to how animators are different from live actors.