- 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 amongt 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?