Colin Morgan often had to stand indoors or in the shade when he wasn't shooting, to avoid looking pale in one scene and tanned in the next.
The ancient jewellery, talismans, and symbols seen in the series were based on artifacts on show in Jorvik Viking Centre in York.
Rupert Young (Sir Leon) was only supposed to appear in one episode. However, fans loved him so much that the writers decided to have him as a recurring character. In season four, he finally became a series regular.
According to cast members, Bradley James is a vicious prankster, with Angel Coulby getting the most pranks from him. Not even Colin got spared of his pranks, even if on-set.
Of the six episodes in which Lancelot appeared, three were named after him.