Node implements the 418 I'm a Teapot status code in a few places. Its source is RFC2324, Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0). Note the title - HTCPCP/1.0 is not HTTP/1.x. HTCPCP was an April 1 joke by Larry to illustrate how people were abusing HTTP in various ways. Ironically, it's not being used to abuse HTTP itself -- people are implementing parts of HTCPCP in their HTTP stacks.