This is a HOT one!
Show a see-through crystal box. When you open the drawer, the drawer suddenly catches fire! To put the fire out, close the drawer. Now the box is magically filled with objects (e.g., bills of various denominations). You've gotten the audience's attention twice!
But that's not all! Open the drawer and remove the objects. The box is entirely empty once again. BUT, suddenly the drawer catches fire once again! Not to worry - close the drawer, the fire disappears, and the box is once again magically filled with objects (e.g., colorful paper flowers).
This looks great, and is an audience pleaser. Really mystifying!