Recently did a blog post (https://www.puppetdude.com/single-post/Character-Development)on developing characters. This was more geared toward puppet team builders, but it got me to thinking:
As a puppet builder, when working on a puppet design, how detailed do you get with the development? Not the physical design, but like the mannerisms, quirks, etc. How much do you take into account when creating? Or do you just work with a design and not really think about the personality?

I feel you have to take the puppets personality into consideration when you are designing and building. A villain is going to have different features then a hero. Where would the Grouch be without his scruffy fur and heavy brow?  A good visual for this is to do a Google image search for Cartoon Villains then compare to Cartoon Heroes. 

If they have quirks or mannerisms it is very possible that you need to construct the underlying structure a bit different. While with a hand in mouth puppet this may not be as critical can be very important with other styles of puppetry like marionettes or rod puppets. The joints may need a bit of tweaking to attain certain mannerisms.

I agree. For a short time I was taking animation in Arizona and it was similar concepts. You just naturally had physical characteristics for certain characters as well as mannerisms.

Great suggestions. Things like that greatly add to the puppet being "believable" in a way, right?

Too often, puppeteers concentrate on the voice more than anything and they lose mannerisms and such which does set the believably.