- The number of episodes in the first season is 9, which is a special number in Norse Mythology. There are 9 worlds in the world tree Yggdrasil (that is spelt with 9 letters in modern English), Odin hung himself from Yggdrasil during 9 nights, Odin knows 18 charms (9x2), Hel was given command over 9 worlds, at Ragnarök Thor will take 9 steps after killing Jörmungandr and die from its venom, Hermondr rides 9 nights to reach Helheim and free Baldr and Ægir has 9 daughters.
- The music that plays during the raid in episode 4 is a "Fehu" by Wardruna, and it's played with the kind of instruments the vikings actually used. The lyrics are in Old Norse and based on Norse and Anglo-Saxon rune poems: "Fe [wealth] causes strife amongst friends, The wolf feeds in the forest, Fe is joy to man, strife amongst kin, path of the serpent, The snake lies coiled, Hidden, it waits beneath, like a frost-covered field, Strife that kinsmen suffer." Ironically, all the parts criticizing wealth are from Norse poems, while "Fe is a joy to man" is from Anglo-Saxon poems.
- Think about the crucifixion scene from Athelstan's point of view for the full Fridge Horror. He's going to die in hideous pain, surrounded by enemies, it could take days, and then what? No heaven for him, because he's an apostate and a killer. No Valhalla, because he screamed in agony and begged for his life, not a brave death in battle. Whichever religion is right, he's getting the bad end of the deal... at least until King Ecbert came along and bought him more time.
- The Vikings' reaction when Athelstan asks them about Ragnarök. Nowadays, we may think this is one of the coolest parts of Norse Mythology. But when you actually believe that all this will literally happen? Just plain scary.
- During Rollo's baptism, Ragnar sees Aelle kneeling and plays along. When Aelle starts to rise, Ragnar hastily scrambles to his feet. As a rival ruler, he would lose face if he were still kneeling while the king stands.
- In the season finale of Season 3, during the siege of Paris, Ragnar, as he lays dying, has a conversion to Christianity and asks to be buried in Christian tradition. His body is carried inside Paris by a small group of soldiers inside a casket. When he is carried inside the cathedral, Ragnar springs out and opens the gates to Paris, letting his army loose inside the city. This is almost exactly like an account of Bjorn's exploits in the siege of Luna. While it could just as easily be dismissed as some of the artistic licenses the show has taken, who is to say that Bjorn simply didn't follow in his father's example?
- Tostig was cool and all, but his role was really minor and there didn't seem to be much point to the character... except as a Foreshadowing of what is likely to become of Ragnar eventually — all his comrades are dead, his nearest and dearest are slowly drifting away from him, and — sooner or later - the only thing he'll have to look forward to is a death worthy of Valhalla.
- Similar to the above, Season 1 made a big deal about how Haraldson used to be a lot like Ragnar in his youth; it's easy to surmise that the burdens of power, the loss of his sons, and the loss of his friends and peers shaped him into the petty, paranoid man that he became. This foreshadows Ragnar's own character development; the loss of his daughter, half a dozen or more friends, being abandoned by the woman he loves and left with a woman he grows to loath, and suffering betrayal after betrayal eventually shapes him into a detached, bitter, contemptuous man who trusts no one.
- Ever noticed how the show grows darker and grimmer with every passing season? Well, it's based on the sagas and they always begin with a group of young men setting off to adventure, fame and great fortunes and end in death, tragedy and destruction. As of Season 4, the trend continues.
- Similarly, Rollo's improving fortunes, or at least the outward appearance of such, echoes the trajectory of Christian legends and propaganda about converted pagan warriors finding their conversion "rewarded" with worldly treasures. Thus, while Ragnar is following the tragic ending of his own saga, with the tone of the whole show following it, Rollo seems to be receiving the Standard Hero Reward in full.
- In Season 1, Earl Haraldson mentions to Siggy that Earl Bjarni(the Swede who he sold his daughter Thyri in marriage to) is a cousin of King Horik. Later, we learn that said king rose to fame by slaying the six uncles who killed his parents. That makes the odds pretty good that Earl Bjarni was the son of one of the six evil uncles....which goes a long way in explaining why King Horik doesn't seem to care about his murder.
- Floki mentions in the very first episode that Bjorn has Ragnar' eyes, and therefore, he will become both like him, and seek to surpass him in fame. This becomes more and more true as the seasons go past. The Fridge Brilliance of this Foreshadowing kicks in when one realizes that the other son who inherited almost the exact same shade of Ragnar's Icy Blue Eyes is Ivar, the son who is most like him, and who will become a Viking more famous than his father as well.
- When Hvitserk kills Bishop Edmund in Wessex, Floki looks uncharacteristically put out by this act. While some of it is no doubt down to character development (see: him defending men praying in the mosque from Harald and his men) Floki himself has killed Aethelstan who was also a Christian who accepted his death with dignity and his own life was thrown into complete disarray as a result. It wouldn't be unlike Floki to ascribe this to divine retribution, and fear that Hvitserk essentially brought it down on himself and everyone else again.
- After Kjetill and Frodi massacred most of Eyvind's family they are seen eating large chunks of meat. Eyvind had no animals with him. Where did they get the meat from?
- When Rollo swears loyalty to Ragnar all they way back in Season 1 he adds "as long as your good fortune holds" to his oath, making everyone listening laugh. Thing is, you cannot accuse him of not being true to his promise.
Fridge / Vikings