A group of Manhattan Project physicists created a tongue-in-cheek mythology where superintelligent Martian scouts landed in Budapest in the late 19th century and stayed for about a generation, after which they decided the planet was unsuitable for their needs and disappeared. The only clue to their existence were the children they had with local women.
The joke was that this explained why the Manhattan Project was led by a group of Hungarian supergeniuses, all born in Budapest between 1890 and 1920. These included Manhattan Project founder Leo Szilard, H-bomb creator Edward Teller, Nobel-Prize-winning quantum physicist Eugene Wigner, and legendary polymath John von Neumann, namesake of the List Of Things Named After John Von Neumann.
The coincidences actually pile up beyond this. Von Neumann, Wigner, and possibly Teller all went to the same central Budapest high school at about the same time, leading a friend to joke about the atomic bomb being basically a Hungarian high school science fair project.
But maybe we shouldn’t be joking about this so much. Suppose we learned that Beethoven, Mozart, and Bach all had the same childhood piano tutor. It sounds less like “ha ha, what a funny coincidence” and more like “wait, who was this guy, and how quickly can we make everyone else start doing what he did?”