In the 80s, I recall Pitfall! (NTSC) having an unusual visual: when standing directly below Harry, the scorpian would alternate between the left facing and right facing characters rapidly, creating a flickering (mirrored) effect. I have not been able to reproduce this. Now, the scorpian simply freezes in place until Harry moves again.
Could it have been the TV? A different ROM version? I attempted to recreate the effect with a switch box on an older television. Does anyone else remember this visual effect?