Hi people I am one of the annimators for team 222 and we are getting ready for our new season and I would be thabkfull if any other animators out there would be willing to share any pre-fabs 
At the risk of sounding out of the loop, what’s a pre-fab?
I know that in WorldCraft (a program for creating levels in games such as half-life) a pre-fab is a prebuilt object which can be placed in the level (like a table or a chair). I’m not sure what it is in 3D Studio MAX or AutoCAD but I’m assuming its something silimar.
If that is what you’re looking for, then check out Ed Sparks FIRST CAD Library at http://sharingfirst.mit.edu/users/edsparks/.
Many people come up with names for different things that sometimes confuse us in many ways. 
Yours for example:
pre-fab: a file that can be loaded over and over again into many projects without causing a complete replacement of a scene but simply a merge into the scene.
Files in 3d studio max that are filtered as .3ds are what your calling pre-fab (slang). Like Jay Lundy said above me, a chair or a table or anything close to that nature. Can be almost any kind of geometry or shape or an edited shape/geometry into a full mesh.