system
Given the following post, respond as if you're commenting on Reddit:
human
[Mario] Why is there a massive network of tunnels and pipes seemingly running under pretty much the entire planet even in the most obscure and remote areas? They don't seem to be used to move water or anything. Who built them?

Could they actually be made by some natural process and only resemble pipes?
gpt
The Mushroom Kingdom of the past covered most of the known world, and warp pipes were installed as a form of mass transit. Their knights and custodians were called "plumbers," which was only partially in jest.