Form and Function: What looks good, and what actually works

 These images from Creative Character Design by Bryan Tillman show how precarious the balance between form and function is. On first glance, the first image looks pretty cool. But upon closer inspection, we realise that the bottom set of arms can't possibly function as they are, as they lack the muscular and skeletal structures to support and move them.

 However, when we add the appropriate muscles, the design starts to look pretty weird:

Where does the balance lie between creating something that is interesting visually but also looks like it works well enough that the audience doesn't question it? It is a subjective question and the answer varies dependant on the audience and the type of media the character is being portrayed through. People may be more willing to accept unfunctional anatomy in computer games for example, as that is the expectation: computer games are fun. However, in a realistic feature film they would expect to see character design that looks like it would actually work.