Designed this in sketchup to mate two other thing files. The Plant topper sits on a green RadShack toggle switch mouinted to the insert. Two other holes allow for buzzer and LED mounting. I printed Tube and Plant at 116% to accomodate the Arduino Micro and 9V, but the insert was printed at 1% smaller and still fit very snug.
Shown with things:
http://www.thingiverse.com/thing:32207
http://www.thingiverse.com/thing:39443
In action:
http://youtu.be/k2CWuS4Hybg
There are many Mario Bros Theme arduino sketches out there... I went with the first one that worked.