If you have never heard of or used John the Ripper, then you most likely have not heard of or used Johnny either. So, what, or who, is Johnny? Well, Johnny is not a who, more like a what.
What Johnny is, is a graphical interface to John the Ripper, which is a very powerful and cross-platform password cracking tool that you probably have installed in your favorite Linux or BSD distribution, or other UNIX-like operating system. Johnny just takes what used to be a command line task and provides a user-friendly interface to it.