Influenza (or "Zaza", as her family calls her), from the book "Asterix and Caesar's Gift", makes a non-speaking cameo appearance in this movie. Justforkix dances with her briefly during the party in the village at the start of the movie.
This and "Asterix and the big fight" (the version without the narrator) are the only two Asterix movies where the Obelix back story - he fell into the magic potion as a baby and it made him invincible - is not mentioned.
The movie is base on the book "Asterix and the Normans" however it extends the plot and uses elements from some other books, notably "Asterix and the Great Crossing" - such us the viking party scene and the joke about Obelix supply, while the scene when Asterix and Obelix dress up as vikings "Asteraf and Obelaf" with Obelix who can't stop laughing about it, resembles the scene from Asterix and the Goths when the duo dress up as Romans "Asterus" and "Obelus".
In the book the movie is based on the Vikings come from Norway and are mainly refered as "Normans" by the Gouls and are only referenced as Vikings on occasion. However the movie makes no reference to "Normandy" and cuts most of the cultural references to Norway. For example the ruining joke about vikings eating everything "A la creame" from the book is reduced to only one reference (taken from the book) when Timandahaf explain to Obelix how to make walrus a la creame.