The seventh Asterix story opens with an explanation that at the time of the Roman occupation of Gaul, there were two kinds of Gauls: Gallo-Romans, who accepted the Pax Romana and tried to adapt to the ways of their invaders; and the indomitable kind, Gauls who liked food, drink, and a good punch-up. Gauls like the kind in Asterix's village.
Nebulus Nimbus, centurion of the fortified camp of Totorum, wonders how to deal with said village, and his right-hand man Felonius Caucus suggests they take advantage of a Gaulish tradition, the Big Fight; two chiefs duel, and the winner takes control of both villages. But who would fight Vitalstatistix on behalf of the Romans? The candidate is none other than Cassius Ceramix, chief of the nearby village of Linoleum, a Gaul who's not only gone Roman, but is forcing it on his villagers (insisting they shave off their moustaches, cut their hair short, wear togas, and drink water from an aqueduct instead of the river that flows through their village). While eager to please the Romans, Ceramix is not eager to fight Vitalstatistix, whose druid Getafix brews the potion of super-strength. So the Romans plot to remove the druid from the equation...
With supplies of magic potion running low, Getafix goes into the forest to collect herbs. Asterix has a nagging concern about the druid's safety and decides to follow him at a distance; Obelix tags along. Sure enough, Getafix is ambushed by a patrol from Totorum disguised as a hedge; Asterix and Obelix come to the rescue, but in his haste Obelix accidentally flattens Getafix with his menhir. Getafix recovers, but has lost his mind and memory, leaving him a giggling shell of his former self who now actually enjoys Cacofonix's "singing".
Meanwhile, the legionaries report back to Nimbus that Getafix has been taken out, and Nimbus relays the news to Ceramix, who goes to the village to challenge Vitalstatistix to the Big Fight... only to turn tail and run when he sees Getafix, alive and in very high spirits. Nimbus decides to send out another patrol to take out Getafix once and for all; meanwhile, Asterix and Obelix are trying to jog Getafix's memory so that he can start brewing magic potion again, but his first effort causes the cauldron to explode and launch into the air, landing on the leader of the patrol from Totorum, Infirmofpurpus. Once extricated from the cauldron, Infirmofpurpus is "volunteered" to spy on the Gauls, and is discovered by Asterix and Obelix when they go to collect ingredients for another attempt at brewing magic potion. Rather than thumping him, they forcibly recruit him as a guinea pig to test Getafix' potions, most of which turn him different colours, and the last of which causes him to float away like a balloon. This last one allows him to escape back to Totorum and report that Getafix may be alive, but he has lost his mind and is no longer a threat.
Asterix and Obelix visit a fellow druid and friend of Getafix's named Psychoanalytix, although their attempt to explain the situation leaves Obelix with a complex about his weight. When they return to the village, Obelix demonstrates how Getafix received a "little tap" with a menhir by flattening Psychoanalytix - wiping his mind and memory in the process. Now there are two druids brewing useless potions for each other. With no alternative, Vitalstatistix trains for his duel under Asterix. Ceramix, meanwhile, is more confident than ever, and plans to use his anticipated victory in the Big Fight as a springboard to challenge every chieftain in Gaul until he is ruler of the whole land; Felonius Caucus suggests to Nimbus that once Vitalstatistix is defeated, they can get rid of Ceramix in the Circus Maximus (Nimbus finds the suggestion so clever that he plans to get rid of Caucus the same way).
On the day of the match, the village goes out to watch, save the druids, both of whom are still Laughing Mad, and Obelix, who is racked with guilt. As the match begins, Vitalstatistix has Asterix go back to the village to collect Obelix, in case things go wrong and they need his strength. But back in the village, one of the silly potions cures Getafix (and, fortunately, he remains cured after Obelix gets the idea that if one "tap" with a menhir wiped his mind, another should restore it). Once the returning Asterix explains the situation, he brews a big batch of magic potion and hurries off to the fight with Asterix and Obelix, while Psychoanalytix - who didn't get to sample the curative potion - leaves in a huff.
When he hears that Getafix is cured and that they have potion to spare, Vitalstatistix lays out Ceramix in one punch and wins the fight. But the Romans aren't going to let the Gauls get away that easily, and attack, thinking that the magic potion is gone. Per tradition, the Gauls thump the legionaries, and during the fight Ceramix is flattened by Obelix's menhir. Vitalstatistix gives control of Ceramix's village back, with instructions not to kowtow to the Romans anymore.
And so, the story ends happily. The Gauls of Ceramix's village return to their Gaulish ways, and the now-amnesiac Ceramix has become surprisingly courteous, and probably the originator of the famous reputation for politeness that the French once enjoyed. Psychoanalytix returns to his practice, having mostly recovered... and his fame makes up for any side effects. As for Asterix and his friends, they celebrate their victory with the usual banquet, as Obelix' complex about his weight proves very short-lived.
Note: This volume sees the first appearance of Vitalstatistix's wife, Impedimenta, though she is unnamed and looks quite different to her next appearance in Asterix and the Chieftain's Shield.
- Accidental Hero: A little boy stands up and salutes the Romans as they enter the classroom, and is applauded for his good behavior by Ceramix. Once the Romans are gone, it turns out the kid was just raising his hand to ask to go the bathroom.
- Amazing Technicolor Population: When Getafix the druid becomes amnesiac, his attempts at recreating the magic potion formula end up as potions turning people into various colours (not always in a single color either). He is thrilled by this.
- Awesome, but Impractical: Ceramix wants to build an aqueduct in his village. When his aide points out the river already runs through their fields and village, Ceramix orders that the river be diverted since an aqueduct makes it look more Roman, then punches the aide out.
- Badass Normal: Vitalstatistix is proven to be this, as he is able to send Cassius Ceramix flying with one punch, similar to what the Gauls do when under the influence of the magic potion... yet he had had none at the time. Oh, and this is after he'd been running from Cassius for what's implied to be a significant amount of time, and yet isn't even the least bit winded or tired, compared to his much fitter opponent.
- Bamboo Technology: The boxing match ends up surrounded by a fairground offering period-appropriate versions of modern fair entertainment, such as shooting galleries with toy catapults and javelins and a wooden rollercoaster.
- Boulder Bludgeon: Obelix tries to save Getafix from the Romans by throwing a menhir at them. Unfortunately, he ends up hitting Getafix instead, and gives him amnesia. Later in the story he also crushes Psychoanalytix under a menhir, and in the final battle with the Romans he can be seen using his menhir as a weapon (and it ends up hitting Ceramix, with the usual results).
- Boxing Episode: The boxing match between Vitalstatistix and Cassius Ceramix is prominently featured.
- Boxing Lessons for Superman: The Gauls always rely on their magic potion to win the day. Asterix has to train Vitalstatistix in jogging (that is, not his shield-bearers to run for him) for him to stand a chance against The Brute Ceramix.
- Brick Joke: Infirmofpurpus' owl, still following him at the end of the album.
- Les Collaborateurs: Gallo-Romans are treated as such by the proudly mustached, hut-living Gauls. By the end of the story, the Gallo-Romans have gone back to entirely Gallic lifestyles.
- Contrived Coincidence: After everything else to cure Getafix fails, the druid ends up curing himself when his playing around with his potion ingredients leads to him accidently making an anti-amnesia potion.
- The Dragon: Felonius Caucus, Nebulus Nimbus' slimy second-in-command who comes up with the plan himself.
- Darkest Hour: Just as Asterix realizes Getafix's potion has returned his memory, another menhir lands on him (Obelix figuring that if getting hit by a menhir caused the amnesia, getting hit again would reverse it). Fortunately, this time Getafix is still himself afterwards.
- Exact Words: Psychoanalytix asks to see the circumstances of Getafix's amnesia. Obelix obliges by dumping a menhir on him, then doesn't get why Asterix is angry at him.
- Foreign Culture Fetish: Ceramix's home (or domus, as he calls it) is a bizarre and hideous architectural mishmash of Gaulish hut and Roman villa. He also wants to build an aqueduct to make his village more Roman... despite the fact that a river already goes through his village.
- Heal Thyself: How Getafix eventually recovers from his amnesia. It's entirely coincidental though as he wasn't actively trying to heal himself; he just happened to accidently make the correct potion.
- Heroic Second Wind: During their boxing match, Vitalstatistix spends most of his time running from Ceramix. Then, when he sees Getafix is cured and their village is thus safe again, it gives him the courage to finally fight back and knock out Ceramix, even without the magic potion.
- Hypocritical Humor: Psychoanalytix first thinks Obelix is the one who came to consult, and deduces that he feels bad because he's too fat, and that there is no reason to feel bad because of that. When Asterix tells him they have not come for Obelix, the druid then comments that he would feel bad if he was that fat.
- Identity Amnesia: Getafix and Psychoanalytix.
- "Just So" Story: Ceramix's post-menhir extreme politeness is said to be the origin of the French reputation for courtesy.
- Mobile Shrubbery: Used by the legionaries. The one in charge has oak leaves on his helmet (an insignia used by modern French generals).
- Napoleon Delusion: One of Psychoanalytix's patients. This being 50 B.C., nobody knows who he thinks he is.
- Nice Job Breaking It, Hero!: Obelix, being too trigger-happy with the menhirs, causes the amnesia.
- No Indoor Voice: Nebulus Nimbus (Langelus in French, after a church bell). He's always TALKING AT THE TOP OF HIS LUNGS. He thinks quietly, though.
- Obviously Evil: Felonius Caucus.
- Ominous Adversarial Amusement: The legionaries refuse to attack until it gets pointed out they have no magic potion and are outnumbered. The legionaries attack... but then one of them notices the Gauls are snickering. The usual Curb-Stomp Battle ensues.
- Running Gag: Every time any of the characters gets knocked out by a menhir, when they come round they are both amnesiac and extremely polite. The exception is when Getafix is hit a second time; presumably he didn't get knocked out. In the case of Ceramix, the politeness becomes part of his personality.
- Shout-Out: Cassius Ceramix. Ceramic is made of clay. Remind you of anyone? He is also the only character in the series to have one name ending in "-us" and another in "-ix", perfectly fitting for a collaborator.
- A picture of Marsupilami is in front of the Menagerix at the fight carnival.
- Stating the Simple Solution: Invoked and defied; Vitalstatistix observes that they wouldn't have a problem in the upcoming fight if Obelix was chief instead of him, considering Obelix's permanent strength, but Asterix notes that doesn't work as it's against the rules of the Big Fight for Vitalstatistix to abdicate in favour of another.
- Tap on the Head: How Obelix keeps describing the accident. And by 'tap' he means 'being flattened by a menhir.'
- Victory by Endurance: Vitalstatistix's plan for the fight is to run around the ring until the Gauls get the magic potion back. However, when he learns Getafix is back, he's so happy at the news and Ceramix is so tired he defeats him by Ring Out without taking any potion himself.
- You Have Outlived Your Usefulness: Nimbus considers doing this trope when he learns that Ceramix plans on challenging the other chiefs and becoming the head chief of Gaul. And then considers the same for Felonius.