It’s December, and as the Christmas elves appear, there comes a startling elfshelfism joke (in abbreviated form), on Facebook today. I got it from Ryan Tamares, who got it from Britannic Xen Osiris Zane, who got it from someone else, and who knows where such memic material originated.
(#1) Yes, Spock on a cock: the science officer of the starship USS Enterprise, riding a monstrously large rooster (across a bleak alien landscape)
To get to the punchline Spock on a cock, you have to recognize the figure of Spock (from popular-culture tv and movie fiction) and also recall that cock — most commonly used for raunchy reference to the penis — is also a somewhat antique or specialist word for a rooster. (As a result, #1 is not only a joke, but also a slightly dirty joke.)
As described in my 12/22/22 posting “Elfshelfisms”, the elfshelfism is a riddle form presented visually, and depends on rhyme (perfect rhyme or half-rhyme), with example punchlines: lemur on a femur, Dolly [Parton] on a tamale, and sonorants on cormorants.