Quine-Generator
Run quine_generator.py and quine_generator2.py with Python3.
Quines (self-replicating programs) have the source code encoded as part of the source code, so it doesn't need to read any file to get the source code. The latter is impossible if the quine is compiled and the source code file is deleted.
After being fed to quine_generator.py, the target program becomes a quine. Now every time you run it, it does whatever it used to do, then prints itself.
If fed to quine_generator2.py, instead of printing, the target program will create a new file identical to itself. The maximum number of copies is 11, but this limitation could be removed.