The intention here is not to speak specifically about "Polish Jokes", but about this type of phenomena. There are excellent Polish Jokes in New York, or Italian jokes in Switzerland, or Irish jokes in England etc. There are sad ones too. To the point where the Polish-American Journal (published in Boston) printed the following in 2009: "Polish jokes started to decline in the USA when Polish Americans put aside their good nature and aggressively spoke out against this Anti-Polish hatred" etc... Admittedly the Polish Americans have some reasons to object to what historically had never been considerate behavior towards them, mostly by the Nazis and the Soviets in the past and the usual stuff immigrants have to hear anywhere, particularly in rough-going New York.
But leaving history aside, who does not like to have a good laugh? Some manage to make others laugh by poking fun at themselves (these are often the best jokes), others need to somehow degrade someone else, preferably when in an audience with similar intent. That's mostly the case with Polish or Italian jokes etc. Anytime a neighbor nation is involved or an immigrant.
In Brazil, many funny jokes are told about the Portuguese, the former colonials here. They are infallibly depicted as inept, not really intelligent or simply old-fashioned. It's an anti-colonial thing. And living in Brazil, the Portuguese one can meet here, one can see, have not always an easy time. Brazilians adore having fun. But they do not laugh so much when an Argentinian tells a joke about Brazilians...
The Jewish jokes I have come across in various countries, often told by Jews themselves, are sometimes of a different nature. The best ones show how clever Jews can be, usually compared to some other religious person or someone of the country where they live. One could say for these jokes that they are an instrument of self-defense. Using humor for that is a very popular thing in the Middle East.

One of the most notorious jokers there is a Turk, known in many other countries as the Hodjia or Mullah Nasreddin. A pendant to the Till Eulenspiegel of the Nordic people and the Dutch. The literature for whom likes this type of reading is quite ample and available in most languages.
What exactly humor is, psychologically, is an interesting subject: To laugh, is a release of energy and at the same time can appear to be a re-charging of energy. Only people with some spare energy can laugh. An exhausted person, even if there is something funny happening, will say "and I did not even have the strength to laugh..."

A "good laugh" is when one expends a considerable amount of energy. And despite this expense, the fact that there is some re-equilibration of energies going on, makes one feel well. The fact of public comics (the Lettermans, Lenos etc.) having success is mostly due to the timing of their presentations. People watching themon TV are usually tired, at the end of their day and welcome a change of mind which, because even if only slightly funny (more often the case than not), it helps them to re-equilibrate their humor (from the Latin, humidity, the state of lubrication of one's psychological machine).
No doubt also there are bigger than just daily cycles between morning and evening involved in humor being appreciated (and produced). It's tempting to think that the "Air du Temps", the flavor of the times plays a role. And if that is the case one might find an astrological link to that. It's quite easy to find a person's horoscope who is often inclined to laugh or gifted to tell funny stories, true ones or jokes he/she picked up somewhere. There are also characters who by simply being what they are, without doing much for that on purpose, are funny.
As a very general observation I found that sun-sign Aquarius is often funny, or fun to be with. A friend of mine, French, ex-captain with the air-born troops in French Africa, then turned banker and a very likable Aquarian has in his horoscope Sun/Jupiter conjunct in Aquarius and an exact trine between Mercury (in Capricorn) and Uranus (in Taurus). He is truly fun to be with. And knowing it, he has made it kind of a standard procedure in his behavior to entertain whomever is in his company. To the point where he had a rich client who accompanied him (on his own expense of course) on many of his professional displacements, just for the fun of being in the Aquarian's company.
Another quite entertaining Aquarian, overtly gay, is a German born in Brazil whose map I made. His natal Uranus (in Taurus) trines his Mercury (in Capricorn), as for the previous person. This leads me to wonder whether a well aspected Mercury in an earth-sign is not bringing about a light element, but also a well "earthed" ability of understanding whatever situation arises. "Funny" is often an observation which is "to the point". There is the unexpected, for whom did not see it by himself, which is being pointed out by the witty person that makes the other one laugh.
What's going on with Aquarians? The fact that they are opposite to the sign of Leo may give an explanation of why they easily can poke fun of themselves, in a light way. Contrary to a Leo, exactly. And that gives them a detached way of dealing with what comes across their path as well. As about themselves. But one better specifies that not all Aquarians are funny or likeable people. Some even show to the outside world the "worst sides of Leo, their opposite sign", i.e. the shadow...
To be more complete, but it's limited to my personal observations as I never came across any astrological take on humor, the map of a young Pisces I made (who is very good at telling stories), has the following characteristics which appear to give him such abilities: Mercury right on his Ascendant in Pisces, enforced by a precise trine from Saturn in Scorpio. His Piscean sensitivity and Mercurial wit is stabilized by a sarcastic Saturn. A way one can interpret his map.
A look at some slow planets and their transits in various signs permits a tentative conclusion which I hope some readers may be able to confirm or even amplify. There were in my experience 2 periods over the last 50 years with more humor and probably jokes being produced and told then other at other times:

The first period strikes me to have been in the late '50s and early '60s. This from what I remember was a period when satirical journals were en vogue:
Le Canard Enchainé in France e.g. had a ball making fun of all-important De Gaulle.
Playboy was at its peak, all over the world, and often man would buy the magazine because of the jokes, they said. Uranus then was transiting Leo. And - I freely interpret, Uranus being in his opposite sign of were he belongs, was loosening up what needed to be, in fixed and often stubborn or grandiose Leo.
The second period was in the mid-'80s. Then it probably was Jupiter who was transiting Capricorn, loosening up "Saturnian things". Possibly that Neptune then in his turn, as he was entering Capricorn, gave a hand as well.
Right now, with Pluto in Capricorn, I have the impression that in general the penchant for jokes and similar light stuff is receding. And the economic shock the world experienced lately has to do with that as well. The idea to investigate at first about "Polish Jokes", and then the rest came from my personal perception that at this moment there is very little joke-telling going on. A local illustration for that: when Lula was running for president here in Brazil 8 years ago, the place was full of jokes. Now it's very quiet. Almost colorless. And from what appears in the French and American press, it's the case there as well. Who thinks that e.g.
The New-Yorker is still funny these days?