I have made NURBS body for the creature I am attempting to create. I have also made a NURBS leg as a separate object. The two objects don't necessarily match parameterization. How can I join the two together. I know I can join them with a circular fillet as two intersecting surfaces. Does it matter that their parameterization may not match when I do this, come render time?
Joining NURBS surfaces together is tricky and sometimes best avoided, depending on the needs of your scene.
I haven't come across too many instances where using things like the circular fillet on a character was a good solution. I think those tools are better suited for sculpting inorganic objects that aren't destined for animation. For a character, polys are usually preferred. If you do go with NURBS, consider using a patch or 'socking' method, where you build the character out of patches that are designed to meet along edges for seamless blending.
If you do go with this approach, be aware of the two main problems you are likely to encounter:
1. surfaces may 'pull apart' from one another when deformed (including by joints)
2. 2D textures will be difficult or impossible to get to flow seamlessly across these joins.