I draw the webcomic Manly Guys Doing Manly Things and work on cartoons you might see on TV sometimes.
I had a couple people asking me about mouth charts, so here goes. I want to preface this by saying that as with everything in art, there isn’t really a “right way” to do them, there are just things that work and things that don’t, and it’s important to understand why the things that work do and why the things that don’t… don’t. Personally, I find it extremely distracting when the teeth pop on and off and create a strobing effect like this;
Again, there isn’t a “right” way to do mouth charts (because some of the best comic effects come from really goofy, unrealistic, or overly detailed mouths) but if I had to guess I would assume this style of mouths came from thinking of the characters as static illustrations before considering what they would look like animated. When you look at a Family guy illustration (such as the ones used in marketing and merchandising), they don’t put any teeth in the mouths
So (and again, this is just an assumption) I think what happened was they decided they liked the imagery of smiling toothless Peter and decided to preserve it by only adding teeth when absolutely necessary. Unfortunately, that makes for distracting speech animation. They probably don’t think many people care that much (which I’m sure they don’t) and have decided it’s more important to make sure he looks as much like the stationary model they decided they liked as possible at all times (this is also the reason you don’t see the same deformation and antics that you used to in shows like the Simpsons).
I think the thing to remember about teeth is that only the lower ones will (realistically) move in your skull. Obviously cartoons aren’t bound to realism and there are plenty of situations where you could throw that rule out the window, but for the sake of learning the rules before you break them; Upper Teeth Are Rooted In Place.
(these are kind of scribbly but I guess they communicate the point)
People have all sorts of different mouths, some people primarily show their upper teeth, some people primarily show their lower teeth, some people are really toothy and show both sets, some are really tight-lipped and you almost never see their teeth at all (there’s a great bit on this in the Animator’s Survival Kit by Richard Williams), but the difference will always be in how the skin wraps around the skull. The lower jaw moves independently of the skull, fleshy parts of the mouth can move independently of the skull and lower jaw alike, but the upper teeth remain anchored.
There are a lot of different ways you can go about doing a basic mouth chart for a character. Almost any animation book worth it’s salt will outline the shapes you’ll need to start with (like this page from Preston Blair)
I’ve worked on shows that had cycles of everything from ten (the absolute minimum that will hit all the phonemes) to twenty mouths for each emotion. Here’s a (somewhat lopsided) chart I made for Blue with 36 frames (18 happy, 18 sad/neutral)
You can get by with one mouth per phoneme, but you can run into problems easing in and out of vowels that way (for example the “sh” that leads into “shoot” is not the same shape as the “sh” that leads into “sheet”) I usually figure out my chosen pallet of mouth shapes, so to speak, like this;
INB just indicates where I would add mouths to ease from one shape into another, how many you add depends on how smooth you want it to be. It gives you something a little like this;
I just kind of slapped this together in an hour or two a while back to test out the mouth, but it looks a little like this when you actually use it to animate with
Again, I cannot stress enough that these are not hard and fast rules and there are as many ways to animate a mouth moving as there are animators to draw them, but this seems to be a decent way to go about getting a solid selection to use for casual conversation that doesn’t pop and strobe.