There's a neat linguistic twist involved with this joke. Word formation via compounding permits the creation of looooooooooong words in German, thereby allowing the hard word in the punchline to be much harder than the hard word would be in an English version of the joke, while at the same time (and this is important!) allowing the hard word to refer to the joke itself in a haiku-third-line kind of way, imho making it an even better joke. In the English versions I've seen, the hard word is just the longest hardest English word the writer can think of, unrelated in any way to the joke; and where it did relate to the joke, it wasn't really all that hard, relatively speaking.
We've all heard of something being lost in the translation, but this appears to be an example that goes even further. I realized that since one of German's special characteristics is the ability to form long words, then it is ideally suited for humor or wordplay or maybe other things that depend upon long words. I'm wondering whether there are other structural characteristics in languages which make some better suited for particular uses.
Later I came across a good example of a German joke that doesn't
translate well into English, this time due to the way that a
people or language categorize things. English bat is
German Fledermaus and English fieldmouse is German
Feldmaus, so in German they're both kinda mousy, but one has
wings...
Eine kleine Feldmaus sieht zum ersten Mal in ihrem Leben eine Fledermaus. "Mami," ruft sie, "komm schnell, da fliegt ein Engel!"
And some time after that, I came across this cartoon, just as funny, but even more obscure for those who don't know German! Or perhaps made less obscure by the imagery...