Source: The Sims
The Sims 4 features perhaps the most powerful character creator in gaming. This tool offers a wide variety of customizable content, including physical features. You can make your Sims wispy thin or sumo wrestler large. Noses can be huge or tiny, hooked or straight, wide or narrow. Mouths can move around on the face. A Sim’s head can be squished or stretched, it’s all up to you.
While all of that variety is of course awesome, it also creates a huge challenge in terms of animation:
Imagine you are creating an animation where a Sim puts her hand close to her hip. In the animation, that hand will have a defined position in space – about three feet up from the ground and one foot over from the center of the Sim. The problem is that the hip on a sumo wrestler sized Sim would be an additional half foot out from where a more slender Sim’s hip would be. So when the Sim plays back that animation, their hand would be buried inside their body.