Could something like this be done or did I watch too many movies?

[bakelitedoorbell]

I think it depends on what type of file is being transferred. For example, if you are downloading an application, the source code would probably have a smaller file size compared to the compiled binary file.

So your downloading tool requests the application, the source code file is sent quickly, and then your computer's software center could possibly compile it for your computer. That kinda meets your definition.

[Cheesemill]

From my experience the source code is always much larger than the compiled application.

For example source for the Linux kernel currently runs to around 470MB, whereas Ubuntu kernel packages are around 30MB.