Pipe Fist

Pipe Fists are enemies in Super Mario Land that appear in the Chai Kingdom. They live in Warp Pipes like Piranha Plants.

Super Mario Land
Only two Pipe Fists appear in the twelfth and final level of Super Mario Land, World 4-3. They behave in a similar way to Piranha Plants, only they move quicker and are immune to Mario's Superballs. Another difference they have is that when one fist goes back into a pipe the other will come out shortly after, making it difficult for Mario to get past them.

Trivia

 * Only two Pipe Fists appear this could possibly be a refrence to the fact that most people have two hands. And that the fists move in a way that looks like there punching.