Hyper Text Coffee Pot Control Protocol

Apparently, there is an HTTP extension which allows you to interact with coffee pots.

Even though it started as an April Fool’s Day joke, Mozilla got a number of bug reports complaining about the lack of support for this protocol.

So, whenever you get a 418 HTTP error, it’s the server saying I'm a teapot

P.S: On 2014, the protocol was updated to support teapots, yay.