The RFC provides specification for a protocol based on HTTP, which can be use to send signal to a coffee maker appliance which can help people make coffee.
Clearly this is intended as a joke, but it is a well-written RFC which has all the details necessary to build HTCP-compliant coffee maker.
and according to this wikipedia entry, is indeed has been implemented on Emacs and Mozilla browser (through 3rd party patches).
Other Humorous RFC ?
HTCPCP is an example of a well written RFC which is intended as an April Fool’s joke, but it is not the only one produced, please refer here : http://en.wikipedia.org/wiki/April_1st_RFC for a list of RFC written specifically for April Fool’s day.