Scoop of the day: Did you know that Manny had a tongue? Surreal, uh?
In an earlier Post, I indicated that lips syncing will be made using the classic stop-mo technique of "replacement mouths" on the puppet’s skull. The very basic set of mouth required for realistic lips syncing is 7 distinctly shaped mouth pieces. More can be made for other facial expressions, but with seven mouths per character, you can realistically animate any dialog script.
Frame by frame analysis of the Intro cut-scene of Grim Fandango shows that the animators were relying on 8 mouth models (or rather textures) with the 7 classics, plus an additional variation on the “E” allowing for more subtle mouth moves (Manny is often talking to himself, and skull-mumbling is easily rendered alternating "closed E" with an "open E" mouth piece).