The Roman Colosseum is repeatedly referred to as the Circus. While Rome had many Circuses, like the Circus Maximus and Circus Flaminus, the Colosseum was not one of them.
During the opening credits of the Walt Disney Home Video VHS release of the film, the title is misspelled as "The Twelve Tasks of Asterisk."
As is the case with many other Asterix movies, the Colosseum is shown during the reign of Julius Caesar, over 120 years before it was built.
When Julius Caesar lists the Twelve Labours of Hercules, several of them are wrong, namely Hercules killing Geryones and Diomedes and Hercules freeing Theseus from the underworld. Hercules killed Geryones while having to steal his cows; when Hercules had to steal Diomedes's men-eating horses he fed Diomedes to the horses; Hercules went into the underworld to capture the multi-headed dog Cerberus, during which he also rescued the captive Theseus.