Quoted from FourFlippers:If you do a Stage/Theater test, or lift the playfield, you'll see as part of the weldment, there's a pinball that's in the theater, welded to a lever. See the diagram from the American Pinball page below:
https://www.american-pinball.com/games/houdini/docs/Stage%20Mech%20Breakdown%20ASM0028-00.PDF
You should post over in the main Houdini thread so Josh can chime in.