Disowned Adaptation: René Goscinny and Albert Uderzo didn't even know the 1967 film was being made until a few months before release, as it was greenlit by their publisher Georges Dargaud and Belvision Studios CEO Raymond Leblanc without asking them. They did not look back fondly at it, and demanded to direct the next one, Asterix and Cleopatra, which ended up better received overall.
What Could Have Been: In addition to Asterix the Gaul, which was already made without asking Goscinny and Uderzo, Belvision Studios was making two other animated films at the same time, based on Asterix and the Golden Sickle and Asterix and the Big Fight respectively. Goscinny and Uderzo ordered to destroy the footage as they were made without consulting them (it was not possible to destroy the footage of Asterix the Gaul as it was already advertised and soon to be released), and they took over for the next project, which ended up being Asterix and Cleopatra.
The film had a Companion Show, a one-hour special titled Two Romans in Gaul. It was written by Goscinny and Uderzo and broadcast on French TV as promotion prior to the film's release in 1967. The Romans and other characters were live action, Asterix and Obelix were animated, making it the first time Asterix and Obelix were animated.