When a sticky piston is attached redstone 1-clock and wool is on top of it, the piston arm will momentarily disappear and the wool will switch colours.
- Attach a piston facing upward to a redstone 1-clock.
- With the clock activated, you may already notice the arm glitching out.
- Place orange wool on a sticky piston to achieve what I have done in the screenshot.
This happens in 1.3.2 also as seen in the screenshot