Since we're talking about the Hyper Text Coffee Pot Control Protocol here, physical attributes of the teapot are irrelevant and thus outside of the scope of the RFC.

The RFC (http://www.ietf.org/rfc/rfc2324.txt) specifically states:

    2.3.2 418 I'm a teapot

    Any attempt to brew coffee with a teapot should result in the error
    code "418 I'm a teapot". The resulting entity body MAY be short and
    stout.