The charter portrayed by Lothaire is called Emperor Charles who has a daughter named Gisela. Based on this information, along when the historical Rollo invaded France, the Emperor in question is actually King Charles the Simple. Charles the Bald ruled from 875-877. Count Odo was Charles the Simple's predecessor as King of West Francia.
One of the birds shown while Aethelwulf is waiting in Princess Kwenthrith's tent is an Eclectus Parrot (native to the Solomon Islands, Sumba, New Guinea, northeastern Australia and the Maluku Islands), which was unknown to European civilizations during the Viking era.
The widespread use of crossbows on the Frankish side is anachronistic. Besides the main factor for Frankish victories against the Vikings was their heavy cavalry, if they could muster it in time and catch up with the elusive and mobile Norse raiders.
Aethelwulf (Moe Dunford) says "Magnus" is a Northen (Scandinavian) name which is untrue.
Magnus is a Latin name with origins in the Roman Empire.