Modern operating systems, browsers, and office suites have become megasystems built on millions of lines of code. Their sheer size can intimidate even experienced users and programmers away from attempting to understand and modify the software running on their machines. This paper introduces system-specific interpreters (SSIs) as a tool to help users regain knowledge of and control over megasystems. SSIs directly execute individual modules of a megasystem in a gdb-like environment without forcing the user to build, run, and trace the entire system. A prototype framework to help write SSIs is described in this paper and available for download at https://github.com/matthewsot/ssi-live22.