If you can put arbitrary content into data to be compressed and don't have any real length limits (<1MB or so, probably) then skewing the probabilities to have

If you can put arbitrary content into data to be compressed and don't have any real length limits (<1MB or so, probably) then skewing the probabilities to have the compressor spit out the data you want is pretty straightforward. I'll write a blog post on that at some point, as it's a technique I abuse in a couple places.