I've never tried motion-capture files on the baby, but some of them should work.

You can find almost 30MB of mo-cap files (some of which are dance files) here:
http://movement.stanford.edu/santa.zip

If 30MB is too much for you to download in one batch, this site hosts many of the same files in smaller packages:
http://www.help3d.com/Motion_Capture/motion_capture.html

After you load the baby from the Library, import a BVH file (File menu --> Import --> BVH motion) and see how it looks. Incidentally, any resemblance between the Ally McBeal Dancing Baby and Poser's infant character is no coincidence.