This will be a walk-through presentation on dynamic exploration of Android apps using JRuby. We'll give an overview of the entire process, beginning with tools to disassemble the package, followed by a crash course in understanding smali disassembly, modifying, and rebuilding APKs. Finishing up with a tutorial on running code from a targeted android package within a jruby session and a discussion on what this allows us to do, such as access APIs restricted to mobile only, extraction of secret keys, and bypassing/calling custom crypto routines. We'll conclude with discussion of popular obfuscation techniques that reversers are likely to encounter when performing this work, and a few quick dives into popular apps to show audience members what to expect.