All Germans Are Nazis: Averted in an interesting way. Nazi Germany and Modern Germany seem to be two separate entities (as opposed to the latter being simply the former after a very thorough makeover), evidenced by the fact that they both can appear in the same comic — wherein Modern Germany is outright terrified of his fascist counterpart. Moreover, Modern Germany is also terrified of being thought of as a Nazi.
Also Germany has a third entity in the form of Prussia, in the sense of Bismarck's creation and the First/Second Reichs, also appears alongside Nazi and modern Germany.
Britain Versus The UK: Subverted in the early comics; "England" seems to symbolise a more British stereotype and wears a Union Jack shirt, but later on Ireland and Scotland show up and he explains he wears it because the Cross of St. George makes him look like a member of the Red Cross. This is either a case of geographical artistic license (Ireland isn't in the UK at all so England really doesn't speak for him) or a rather weird Genius Bonus (the Union Flag is a combination of the English, Scottish and Irish crosses — but the Irish cross has long since fallen out of use and been forgotten about in both countries). Soon the comic switched to England wearing just the Cross of St. George, though Humon claims to have made the switch because it's easier to draw.
Done quite literally with the "Sisters", who are basically female versions of their "Brothers", with the exception of Sister Sweden and Sister America who represent separate stereotypes.
There are some exceptions: the women are the "main" versions of Mexico, France, and the Baltic States, presumably each with a Spear Counterpart. And the sisters tend to address each other by country name alone. To themselves, they are the main ones and the brothers are the Spear Counterparts.
You can basically tell if a character is a Distaff Counterpart based on whether they have a title/prefix or not (Brother/Sister).
Some Russia has no sister, only Mother Russia.
New Zealand (though she's a sheep), North Pole, and Sami seem to be singular females, while generally the micro-countries/provinces are singular as well.
Don't Explain the Joke: Played straight and inverted at the same time. Yes, Humon usually adds an explanation for the comics which don't sound half as funny when read out aloud, but generally are an utter necessity for people who aren't natives of the countries depicted in a given comic strip. And sometimes even if they are.
Dunce Cap: Norway and Denmark wear them in Sweden's version of the 2011 Norwegian butter crisis strip: here.
Eagleland: While America certainly has most of the Flavor 2 traits, he does genuinely want to help others and is seen as the peace keeper when things get too out of hand. Essentially he's a Type 2 who aspires to be Type 1. Sister America, on the other hand, is 100% Type 2.
The picture of the Canada siblings in swimwear. Let's just say... body hair. This was largely the point, or at least to point out that the author thinks the disgust of it is largely ridiculous. Then again, some of us like a bit of fluff.
Fanservice: Let's just say there are a lot of strips where the characters are more detailed than usual...
Female Gaze: Once when asked why, if she is a feminist, most of her characters are male, Humon replied that as a (mostly) straight woman, she likes drawing men for herself to ogle. She has also expressed irritation with fanworks that present/describe all the male characters as Bishōnen, since she went out of her way to depict numerous different types.
Surprisingly not an America-only trait. The Scandinavians don't know anything about South America, America mixes up Sweden and Norway while forgetting Denmark, and Sister America thought Scandinavia was a country till she discovered the joys of shipping.
Half-Identical Twins: Most of the sisters look just like their male counterparts, but with longer hair and no facial hair. It's most pronounced with the Denmarks, where the sister even has boyish features and a skinny figure.
In one strip, America keeps mistaking Norway for Sweden and can't seem to see Denmark, implying that he is that oblivious. In the last frame, we see things from his perspective: Norway and Sweden look identical, Denmark isn't seen... but we see South America standing beside America, when he wasn't visible earlier! Seems like America's not the only one with selective blindness...
Incest Is Relative: America has a lot with Canada, who is his adopted brother; England is America's birth father and adopted Canada from France.
Laser-Guided Karma: Finland shoves Åland and Sweden off the end of a dock into the water. Two panels later, Åland comes back up screaming that he found a bunch of old 18th-century champagne bottles that are worth a fortune, and proclaims to Sweden that "we'll keep one and open it on the cruise trip I'll be taking you on around the world!"
Mistaken for Racist: In one comic, Denmark mistakes South Africa for a monkey, causing South Africa to attack Denmark. This stems from the stereotype that all Danes are racist without realizing it.
Most likely, it is also a reference to this where a Danish TV host mistook a picture of an African man for a monkey. Also, far from all Danes are racist but are often seen this way because the most racist political party in the country is also the (arguably) most influencial one — plus that whole thing with the drawings.
Norse By Norsewest: Being a comic about stereotypes, each character shows varying shades of this trope. The classical Hollywood stereotype isn't that prominent, however, due to the stereotypes coming from a Danish viewpoint. The comic's premises actually inverts this, as it shows the Scandinavian perception of other countries.
Patriotic Fervor: Inverted with modern Germany, who doesn't like flying his flag around since it might make his people prideful, but played straight with the Scandinavian trio, seeing it as a symbol of joy and happiness. And when it's someone's birthday. Played straight with America.
Really Gets Around: Sweden has slept with every member of Finland's family, and one of them wasn't due to alcohol. His sister's kind of the biggest skank in time and space too. However, a removed comic stated that Denmark is the country that has the most sex, and to date he has slept with Norway, Sweden, Sister Sweden, Sister Australia, quite possibly Netherlands and maybe even Germany.
Real Men Wear Pink: Finland and Sister Sweden enjoy using a strap-on. Finland seems to hold no shame in this, and no one else is brave enough to mock the knife wielding sociopath about it.
Vague Age: All the characters to an extent, but Denmark in particular. He mostly looks and acts like he's in his early to mid-20s, but he has two kids, one of whom is clearly a teenager. Also, he is either the oldest or the youngest of the Nordics depending upon whether he is viewed as a political or a geological entity... yeah, it's complicated.
Wearing a Flag on Your Head: People wear flags on their shirts. In fact, every article of clothing and cloth item the characters own bears their respective flag design, including royal crowns and bed pillows.
Humon frequently makes journal entires giving details about the characters, but also tends to delete them shortly afterwards because she likes to let the viewers find out about the characters themselves, not by some Informed Abilities.
Also, there's much debate about the sexuality of the characters. So far, the only confirmed facts are that Sweden is gay (currently in a relationship with nearby island nation Åland) and that Finland is straight (in an on-again-off-again relationship with Sister Sweden). She also stated that she does not think the characters are actual embodiments of the countries like in Axis Powers Hetalia, but more the personifications of the inhabitants of those countries.