X-Fry / X-Bender
loreSlashdot's response headers carrying a random Futurama quote, named for the characters who said it.
For years every response from slashdot.org included one extra header, X-Fry, X-Bender or X-Lrrr, whose value was a line from Futurama chosen at random per request. Nothing read it but the people who ran curl -I against the site, which on Slashdot was a fair share of the readership. It is the purest form of the easter egg header: no purpose, no recruitment, a joke addressed to exactly the audience that would get it. The How-To Geek write-up that catalogued hidden headers used it as the opening example, and a commandlinefu one-liner existed solely to fetch a fresh quote.
Also known as: X-Fry, X-Bender, X-Lrrr, Slashdot Futurama headers