Not familiar with the gag but perhaps the display segments cut out with foam core panels behind them. paint he foam core the same color as the face of the segments and 'paint' the time you want. top of each scene just slide out the foam core and load another behind it. Does that make sense? Again. I'm not familiar with the gag, I'm assuming this is a big oversized thing. If it's small I'd adapt the same idea but build a system with an acetate scroller in it; either manually operated or driven by a stepper or solenoid motor.