An anvil on a Pisten pushing upwards with a Redstone clock causes the anvil to glitch out and go all over the place, even inside the extended piston arm.

How to do it in steps

   Step 1: Make a Redstone clock with 2 repeaters on 1 tick facing into a block going into a square loop. Then from there, you make 4 repeaters go straight from one of the blocks feeding into a regular piston facing upwards.

   Step 2: ad the anvil on top of the face of the piston

   Step 3: Ad a lever and quickly flip and un flip it to cause 1 Redstone tick signal to go into the Redstone clock feeding into the piston.

There is a gif of it happening in action in the attachment below.