Batch auto-renamer?

This is a little obscure, but I need to dummy many large batches of files, and the sheer amount of them means it would take AGES.  When I say dummy, I mean I want to for example take these:

Alpha.jpg, 356kb
Beta.jpg, 874kb

And I want to replace them both with a "dummy" jpeg file 1kb in size, so that I'd end up with Alpha.jpg, 1kb and so on and so forth.  Is there anything that will automatically take my files, dummy them, and rename the dummies like the originals for easy replacement?  I'm sure someone must have thought of something like this at some point or another.  Help, please--I've got to do this on such a large scale that I'll be renaming until next year.

it'd be easy using bash, python, or even php. If you're on windows, well....good luck with that :) Find someone knowledgeable in one of those languages, and ask them nicely :P