Hey clam61 yes 3D animations are in specific file formats that a 3D engine would interpret and render. You can use 3D software tools such as 3DS Max, Maya, Blender, etc. to create 3D models. You can then rig your mesh with bones and constraints to bend and position your mesh. It's been awhile since I've messed with 3D models, but I believe they were .obj files and .MD2 files I used. It was for an Away3D project.
As far as incorporating these into Sparrow that would be a nightmare mixing Sparrow with a true 3D engine. You'd be better off just using a 3D engine.
As far as getting 3D animations into Sparrow, you can fake it. I'm doing the very thing in a game I am working on. My designer has built 3D animated models in Blender. All our animation sequences are exported as movie files (.mov or mp4). You can then use Flash to build a SWF file from the movie file since its just frames. From there you can use Flump (http://threerings.github.io/flump/) which will execute your SWF and generate a texture atlas with some XML that defines keyframes. The nice thing about Flump is it's really smart about re-using textures. Instead of having a single texture for every frame of your animation, every texture is re-used and the XML file defines how the next frame should be interpolated. So each frame is built from a re-used texture that is just scaled, skewed, rotated, and positioned. I wrote a Sparrow extension for Flump awhile back if you want to check it out. https://github.com/levieggert/SXFlump I have an updated version as well that hasn't been uploaded.
I also came across this, I think it does the same thing as Flump. (http://gafmedia.com/converter/) But, I like Flump better and I already have a run time for it.
Hope that helps!