Antoine Maréchal (Bourvil) is leaving Paris to go on holiday in Italy when he has a car accident with Mr. Saroyan (De Funès). He thinks his vacation is ruined, but the next day Saroyan offers him to drive a Cadillac from Naples to Bordeaux. Actually, Saroyan is a mob boss and he has hidden heroin, stolen gold and precious stones, including the biggest diamond in the world, the Youkounkoun, in the Cadillac.
The Sucker provides examples of:
- The Alleged Car: Maréchal's Citroën 2CV, which breaks into pieces after Saroyan's Rolls-Royce bumps into it.
- Bat Deduction: Maréchal suddenly guesses where Saroyan hid the "Youkounkoun" diamond in the Cadillac he had to drive:Maréchal: For sure! There are 2 Ks in "Youkounkoun", like in "klaxon"! (which is the car horn)
- Book Ends: The movies starts with a car accident (Saroyan's Silver Cloud crashes into Maréchal's 2CV). It ends with another car accident (the Cadillac avoids a police car but crashes into a shop window).
- Butt-Monkey: Maréchal. His car is broken into pieces. When he tries to pick Gina up, he receives an ill-treatment from the barber, her fiancé. When he dines out with Gina, the waiters constantly make him fall from his chair. He falls from a cliff into the sea. Finally, he is arrested.
- Catchphrase: Whenever Maréchal seemingly manages to display some form of cleverness, Saroyan often says "Il m'épate, il m'épate, il m'épate!" (i.e. "He impresses me!")
- Checkpoint Charlie: Mr Saroyan crosses the Italian-French border. The police and the customs make a thorough search in his car. Then Maréchal also crosses the border. His car is searched too, but nothing is found.
- The Con: Maréchal, an honest and naive guy, meets Saroyan, a mob boss. Saroyan tries to make him drive a car full of heroin, of stolen gold and precious stones from Naples to Bordeaux, without him knowing. Maréchal ends up realizing what happens and sets up a reverse-con to turn the tables on Saroyan.
- Cool Car: The Cadillac, of course (a Cadillac Series 62 Deville Cabriolet 1964). Other cars are worth of notice: Saroyan's Rolls-Royce Silver Cloud and green Jaguar Mark 2, the stolen Rolls-Royce Phantom I, and the red Austin Healey 3000 driven by the Italian mobsters.
- Corrupt Corporate Executive: Saroyan presents himself as a general manager of a trading company but he is in fact a mob-boss who is looking for a "mule" in order to carry various drugs and jewelery through the Italian Frontier.
- Crouching Moron, Hidden Badass: Since Saroyan is a gangster and a mob-boss, he is more than eager to use guns to kill his rivals and karate-chops a statue by mistake when he feels someone put a gun to his back.
- Dramatic Irony: Played for Laughs. The viewer knows Saroyan's plan, whereas the protagonist, Maréchal, does not know it. So the viewer realizes that Maréchal loses the golden bumpers and the battery full of precious stones. The viewer also knows that the Napolitan mechanic has just stolen the two golden bumpers, when Maréchal praises his honesty.
- Eiffel Tower Effect: Some of the most famous monuments of Italy (the Trinità dei Monti, the Colosseum, the Leaning Tower of Pisa...) and the medieval city of Carcassonne feature prominently in the film. Justified, because Antoine Maréchal is supposed to be on vacation and to visit places of interest.
- Europeans Are Kinky: For the French, Northern Europeans are kinky. Ursula, the German tourist, rarely wears more than a swimsuit. Plus she is a naturist and she enjoys skinny dipping.
- "Everybody Laughs" Ending: In the end, Saroyan whispers something in Maréchal's ear, then they burst into laughter.
- Everything's Sparkly with Jewelry: The Cadillac contains precious stones in the battery and the biggest diamond in the world, the Youkounkoun in the car horn.
- Fiery Cover-Up: Saroyan draws a plan to show his men where he hid the contraband, then burns said plan. But unbeknownst to him, a mole had slipped self-duplicating paper under the tablecloth.
- Foreshadowing: The horn of the Cadillac has a problem: it starts honking several times and Maréchal cannot stop it. This is probably because a huge diamond is hidden inside it.
- Gas Siphoning: Everytime Mickey throws sugar cubes in the fuel tank of Saroyan's car, Saroyan orders one of his henchmen to siphon the tank.
- Gratuitous German: Léopold Saroyan tries to warn the German passenger of Maréchal that the "pretty boy" who has joined them is in fact a gangster.Saroyan: Der Beau Garçon is ein salopard. Ein gross salopard!
- Manipulative Bastard: Saroyan, who manipulates Maréchal.
- Mickey Mousing: The car-fixing scene is set to Rossini's Tarentella.
- Mister Big: During the whole trip, Saroyan is aided by two henchmen and he is a Mob-Boss.
- Ms. Fanservice: Ursula (Beba Loncar), the German tourist, who rarely wears more than a swimsuit.
- Muscle Angst: When following Maréchal in the camping site, Saroyan takes a shower next to a very muscular guy who is flexing constantly. After he tells him to buzz off, he tries pathetically to imitate his poses.
- Operation: Jealousy: Both Gina and her fiancé provoke each other: Gina dates Maréchal. When her fiancé sees her with him in a restaurant, he kisses a girl, then dances languorously with another one. Gina then grabs Maréchal's hand and caresses it.
- Orphaned Setup: In the end, Saroyan tells Maréchal that he will get the reward for finding back the Youkounkoun, then he whispers something in Maréchal's ear. The viewer cannot hear it, but it must be very funny because Saroyan and Maréchal burst into laughter.
- Pec Flex: In the campsite showers, Saroyan meets a very muscular guy who flexes his muscles in a attempt to charm him.
- Percussive Maintenance: Maréchal has to resort on kicking the Cadillac to stop its car horn from honking uncontrollably.
- Rambunctious Italian: Gina and her fiancé are introduced when they have a very loud argument. They are both hot-blooded: they both play Operation: Jealousy against each other.
- Refuge in Audacity: When Saroyan's associates are legitimately concerned by the risky move of giving such a huge loot on a random "sucker", Saroyan defend himself by pointing out that Maréchal is such a Ridiculously Average Guy that he is beneath all suspicion:Saroyan: Listen to me, damnit! For such a huge shipment, we needed someone who is naive... He doesn't suspect anything! [...] I hired him at the last moment because he is an honest man... you can see it on his face, and it is the best passport because, remember, at the customs it's the man who is suspicious, not the car...
- Road Trip Plot: Maréchal drives a Cadillac from Naples to Bordeaux over the course of the film.
- Running Gag: The horn of the Cadillac starts honking and Maréchal cannot stop it.
- Shout-Out: One of Saroyan's associates advises Maréchal to read Promenades dans Rome by Stendhal. Maréchal answers that he already has the Michelin Guide (a guide book).
- Skinny Dipping: Ursula wants to go skinny dipping and she suggests Maréchal to go with her. He does not want to, so she goes swimming alone, but soon Mickey joins her.
- Slobs Versus Snobs: Maréchal is a lower-class man, while Saroyan and his associates are rich and cultured. This contrast shows up in particular in the beginning of the film: Maréchal drives a 2CV, while Saroyan drives a Rolls-Royce. In Saroyan's office, Maréchal is astounded by some gadgets. When he eats with Saroyan and his associates, Maréchal turns out to be less cultured than them.
- Spanner in the Works: Maréchal unintentionally ruins a large part of Saroyan's plan: he loses the golden bumpers and he throws the battery full of precious stones in the sea without even realizing that there were gold and precious stones.
- Speech Impediment: Mickey, the Italian mobster, has a stammer.
- Stick 'em Up: During a gun fight against the Italian mobsters, Saroyan walks backward into the pointed finger of a stone statue, which he mistakes for a gun. He drops his own gun and raise hands, before swirling around and trying a karate-chop on the statue's arm — to painful results.
- Too Good To Be True: Léopold Saroyan Offers to the "sucker" a Cadillac and all expenses paid as a compensation for his broken car.Saroyan: Do you still have the intent to go to Italy?
Antoine Maréchal: I don't know if you are aware that my car had an little accident yesterday...
Saroyan: That's exactly why i phoned you this morning. [sits down in his chair] From the beginning... you were looking pretty sympathetic to me... and I had an idea that might fix everything...
Saroyan: We are August the 14th, the car must be at Bordeaux the 27th. [...] Here your ticket for Paris-Naples and 500,000 liras.
- Took a Level in Badass: Maréchal does not realize that he is manipulated by Saroyan for most of the film, but after crossing the French border, he understands everything and he manages to manipulate Mickey and Saroyan. He also hands over Saroyan's henchmen to the police. Finally, he even guesses where the Youkounkoun is hidden.
- Train Escape: Type 1. On the road to Carcassonne, Maréchal manages to cross a railway track just ahead of a train. Saroyan, who was following him, gets caught by the train.
- Vehicular Sabotage: Mickey throws sugar cubes in the fuel tank of Saroyan's car twice to prevent him from following the Cadillac.
- Very Loosely Based on a True Story: The plot is based on the case of Jacques Angelvin, French TV host, who was arrested in the US in 1962. He had carried drugs hidden in his car.