There are several recurrent symbols in the Kraina Grzybow series and media.
"Upperapple, Mushroomland and Paper."
Mushrooms
A very popular family activity in Poland is Mushroom hunting. There are huge dark forests in Poland and this allows mushrooms to grow. There are also apps that can identify the different types of mushrooms. Agatha could have gotten lost in the forest, and this could be why Agatha’s mother is always looking for her. This also could be why Malgosia the squirrel is a squirrel, because squirrels are plentiful in forests, and why there are some visuals of insects, and in PU #4 there is a camera view of trees going around in circles. So, Mushroom land could not be about Magic mushrooms at all.
Apples
"Apfel."
Apples in the series have a connotation as mushrooms. This began in the first episode where Maggie tells Agatha that the "Apple" she's been "Eating" is actually a mushroom. This gives rise to the theory that Agatha is on drugs, specifically Psilocybin Mushrooms, which are known to cause hallucination. When the apple is shown, it always has that connotation. If you were to replace "How to Effectively Apple" with "How to Effectively Shrooms," it would make far more sense. When Agatha is trying to eat the Apple, she doesn't just eat it. She explains there is "Upper Apple (The skin)," "Mushroomland (The part with the drugs)," and the "Paper (Tasteless inner part)", then proceeds to put it in her mouth, chewing it distastefully. She hallucinates wildly, then as it begins to die down, she thinks again, but feels depressed until Maggie (?) cheers her up, and shows her that she was high the whole time and that that "Apple" was actually a 'shroom the whole time. Later on, during "The Apple Escape," Agatha has to wander streets in a kind of "Withdrawal" state, depressed and tired, toking for enough wild "Apples," just growing on the ground LIKE MUSHROOMS to give her the high she needs, all while not being caught by Maggie-3000s (Ed note: I think they're police). The Facebook post on December 23, 2016 shows her in a high again on a vacation with Maggie, but not as strong a high as before, as she notes she is still not happy as before. We will have to wait and see.
Cow
The symbolism of cow could possibly be because “magic mushrooms” grow in cow poop.
The cow symbology can also be about genetics. There is some footage in PU #2 of black and white cows. Black and white cows are created by a white cow and a black cow. This could be a reference to World War Two where Hitler wanted a concrete ethnic group of people by genetics and black and white cows are a mix. This would be a reference to the ethnicities that hitler did not want, and this would also connect to the hidden messages of shelter and the Cold War throughout Kraina Grzybow.
Flowers
Flowers could be a reference to the doctor scene in PU #5 where the doctor tells Agatha she is “Almost fully reflowered.” And this could be a reference to being deflowered meaning a loss of virginity. This could also link to the menstration animation in PU #1.
Dog
The date 09 21 1994's Chinese year animal is the dog.
Dogs also could be a reference to the Russian dog experiment film called "Experiments In The Revival Of Organisms" -1940 where the Russian scientists decapitated a dog and then brought the head back to life by attaching it to tubes and a blood pump which circulates the blood and creates oxygen in the blood, therefore making the dog's head completely responsive. There is even a similar diagram of this shown in PU #5. This experiment and other experiments shown throughout the video have saved injured people in the war. This information would link to the Nuclear War theory. [Which war was not stated. [Most likely WW2.] A Person on a thread discussion on Kraina Grzybów thought of this reference.
This would also link to: "Dog Test" from PU #5.
Prism
Prisms make an appearance in Smile Guide: The Apple Escape. The significance of this symbol is yet to be revealed, but prisms can be found all over Mushroomland.