A delightful collection of HTTP Status Cats includes the above cat-in-teapot came from HTCPCP "The HyperText Coffee Pot Control Protocol" [RFC 2324].
The IETF regularly each April 1st also publishes humorous specifications (as "Informational" documents), perhaps to make the point that "Not all RFCs are standards", but to also provide humorous fodder for technical debates.
The target of HTCPC was the wave of proposals we were seeing for extensions to HTTP in the HTTP working group (which I had chaired) to support what seemed to me to be cockeyed, inappropriate applications.
I set out in RFC2324 to misuse as many of the HTTP extensibility points as a could.
But one of the issues facing registries of codes, values, identifiers is what to do with submissions that are not "serious". Should 418 be in the IANA registry of HTTP status codes? Should the many (not actually valid) URI schemes in it (coffee: in 12 languages) be listed as registered URI schemes?