Big Fancy House: In the manga, the Nordics gathered for lunch and Iceland's "announcement" in a house that looked pretty average-sized. In the anime, said house is much bigger. It's not clearly stated who it belongs to, either.
In the manga and third interval CD, the 'house' is actually a bar at Sweden's place, so it is safe to assume the same for the anime.
Former Teen Rebel/Retired Outlaw: Sweden, Denmark and Norway are considered this after their old Viking days. A discussion about Valhalla even mentions that Denmark wouldn't have minded going there when he was younger, but confessed he would rather retire by a countryside if he could in modern times.
Stockholm Syndrome: A possible and quite cynical take on Sweden and Finland's relationship. Subverted due to Sweden's Gentle Giant nature, which is quite different from the historical take of their relationship. Others speculate that it actually goes both ways...
A Match Made In Moss: Like with Finland, a take of Stockholm and Lima is viewed with Norway and Sweden during their third union. Where Sweden tried to invoke Stockholm Syndrome on Norway only to fall into Lima first. Norway in turn knew Sweden tried to do this, only to warm up to him when their union became a more equal relationship.
Adaptation Dye-Job: Has light blond hair and violet eyes in the manga. In Season One to Four, his hair is the same yellow-blond shade that England and France have, while his eyes are dark brown. His hair and eye color were changed that of the manga in Season Five onwards.
AffectionateNicknamer: Out of the Nordics, he gives the most affectionate titles toward the others. Su-san (Sweden), Ta-san (Denmark), Ai-kun/Ice-kun (Iceland), and Noru-kun (Norway). The other Nordics call him "Fin" in return.
The Alcoholic: Other than Denmark, he is arguably the second heaviest drinker of the Nordics, complete with Alcohol Hic in the Nordic Five Drama CD. If it isn't beer, Fanon does have him drink vodka if given the chance.
Beware the Nice Ones: "Even though he appears to be all soft and mellow, you wont wan't to mess with him!"
Wimpification: Poor Finland may be the biggest victim of this in the APH fandom, after England and Lithuania.
Thankfully a good amount of the fandom prefers to write him as Bad Ass, or take a third option and make him a Cute Bruiser who's mostly nice, but unafraid of facing people when he's upset or his friends are threatened.
Adaptation Dye-Job: He usually has light blond hair in the merchandise and illustrations, yet the anime series initially gave him sandy brown hair and changed his blue-green eyes to a deep brown. This was thankfully corrected in later episodes to him having only brighter blond hair and purely blue eyes. Season 5 changed his colors once more, to match his manga color scheme.
Affectionate Nickname: The other Nordics call Sweden by a shortened version of his name (Su-san, the Japanese name for Sweden is Suuēden) in one webcomic, which was translated by fan scanlators as "Sve" (short for Sweden's name "Sverige" in Danish, Swedish and Norwegian). Since then, many fanworks have Finland or Denmark calling Sweden "Sve" regularly.
Iceland alternatively calls him Sví, from Sweden's Icelandic name: Svíþjóð.
Emotion Suppression: It's said that he's actually overcome with emotions, though he never lets them show.
Face of a Thug: His height and serious face scares everyone. Even if he doesn't intend it.
Gentle Giant/Real Men Wear Pink: Sweden looks like a huge and scary Big Guy... but is very domestic, an excellent babysitter and even sews his old clothes personally before giving them to Finland when the other remarks on their height difference.
Hot Dad: Well, adoptive dad for Sealand and apparently Ladonia, but still.
Although it's smaller one, he's also seen smiling at Finland at the end of the Polish-Swedish Wars strip.
The Rival: Toward Denmark. Truth in Television considering the two countries' history of war against each other have rivalled England and France.
Single-Target Sexuality: Apparently, Himaruya's old notes say that he's "gay for Finland". It may stand from a Finnish stereotype that all Swedish men are gay, dating back from the period when homosexual activity was legal in Sweden while still outlawed in Finland.
Stoic Spectacles: He speaks in a grunting dialect, rarely changes his fearsome facial expression, and scares pretty much everybody when they first meet him.
When He Smiles: The only time he was ever seen smiling was when he adopted Sealand (shown here, scroll down to the bottom of the page), and it was adorable.
"No matter how I see it, you guys do look like brothers. You know, the way you're weirdly scary, and how you have weird friends. And to begin with, we're all something like brothers. And I am the elder brother... WAH!""
Blood Knight: He just won't back out from fighting Sweden. Also, when Sweden was under his rule, he seemed to have a huge grin on his face while challenging Russia.
Boisterous Bruiser: He's often depicted as such in fanworks. Considering how he's shown drinking beer in one of the two strips he's been in and how loud he is in his opinions (to the point that Norway strangles him with his tie). It's pretty much confirmed here..
Can't Hold His Liquor: Seemingly drunk even while sober. Ironic, seeing as he is the heaviest drinker in Northern Europe.
Himaruya also listed in a blog post of his possible first names being "Abel", "Mikkel", "Magnus", "Simon",or "Bertram", and Danish Patronymic surnames, "Andersen", "Christensen", "Arnesen", and "Densen".
Hot-Blooded: Evident when his eyes and right hand were glowing over his excitement on the Nordic Club's furniture making/design discussion activities in the Hetalia World Academy strips.
Volume 5: He's the fireball of energy of Northern Europe!
Selective Obliviousness: It's suggested that he ignores any aggressiveness in the air in favor for a cheerful demeanor, as shown when he happily wishes luck to Belarus' group in Hetaween 2011 after she just threw a hanger at him and declared that their group would win.
Volume 3 (on Denmark): "Poking England, using Russia as a shield, he's quite the active young man. I feel like his personality will turn out to be the complete opposite of his outward appearance."
Add the notes that was listed during the final page of 2010 Bloodbath. Himaruya stated the next time he appears, it won't be in a positive light. Then again, this isHimaruya we're talking about: he often says/writes things and then puts 'em on the shelf.
Fan Nickname: Fan-given commonly have him referred to as "Norge" in fanworks, especially from Denmark (which is, by the way, the term for Norway in Danish, Swedish, and Norwegian.) Norwegian (bokmal) at least. It's "Noreg" if you swear by Norwegian (nynorsk). Noreg is, by the way, the term for Norway in Iceland and the Faroes, apart from the Nynorsk variety (who got it from the western isles).
Himaruya has stated possible human first names for Norway, including "Lukas", "Børre", "Bjørn", "Kjetil", "Knut", and "Sigurd". "Bondevik" and "Thomassen" were listed as his potential surnames.
Idiot Hair: He has a floating one on the side of his head. It's hinted the hair represents his fjords from the Volume Four thank you postcard.
The second Hetalia Fantasia CD has him similarly choking Denmark when the latter suggests that him trying to get away from Germany and Japan is because he wants to be alone with Denmark. They're definitely verging on Vitriolic Best Buds or Ho Yay at the very least by this point.
Norway's Profile: His hobby is poking at Denmark in a strange way.
Confirmed as of the Nordic Drama CD, with Finland thinking that they get along very well despite appearances, and Sweden going so far as to agree and compare it to his and Finland's relationship.
Finland: But I don’t think it means that Nor doesn’t like Denmark. Whatever happens, it seems like Nor spends a lot of time with Denmark.
There are split of fans that make him either a tsun-tsun or dere-dere toward Sweden as well.
"It'd be great if there was stuff like mythical phantom residents that live only in Iceland..."
Adaptation Dye-Job: Received blue eyes in World Series, though he also initially had them in the earliest manga illustrations. In Beautiful World (season 5), his eyes are changed back to purple, but his hair is now blond to match the other Nordics instead of silver.
Breaking the Fourth Wall: He has an awareness of the fourth wall audience. He introduced himself in the beginning of The Movie. Mentioned to the audience if they expected him to do something in the "Making a Good Product in Northern Europe" strip. And during Hetaween 2011, after commenting about the other Nordics acting like kids, he looks behind him and tells the audience to stop staring at him.
Cross-Dressing Voices: Averted and Jossed. A popular and old rumor was that he would be voiced by Mitsuki Saiga, while fans often assumed that a female would eventually voice him anyway. His voice actor for The Movie wound up being a relatively unknown male one, Ayumu Asakura.