Although mobile-based prototyping platforms are numerous, there are currently no tools that support Wizard of Oz interactions on Android. This paper describes a Wizard of Oz prototyping system for Android, via which a designer can enhance digitally generated mock-ups or scanned-in paper sketches with interactive widgets and automated screen transitions. Screen transitions can be based on user action such as a button presses, triggered manually by an experimenter observing from a laptop or triggered based on the user's location or the time. We have integrated scenario-based user testing, a context in which Wizard of Oz testing is often used, by providing support for location-and time-based display of videos and screens in the prototype. It is our hope that this system will find wider use in the design community.