It's a heist movie about a bunch of small-time crooks and hoodlums who plan a caper where they will rob a pawn shop. The idea is that they will enter the neighboring building via the coal chute, sneak into the basement, make their way from the basement into a courtyard, climb up to and over a roof, and then enter the pawn shop via a vacant apartment.
Unfortunately, the gang is a bunch of idiots, and nothing works out.
Marcello Mastroianni appears as Tiberio, a photographer who joins the caper because he's broke and needs cash. Claudia Cardinale had one of her first big parts as Carmelina, sister to gang member Michele, who has a romance with another gang member, Mario.
- And Starring: Mastroianni gets a "with" credit at the end, and the guy who plays Dante, a very famous Italian comedian who went simply by "Toto", gets the exotic credit "and special participation".
- The Blade Always Lands Pointy End In: Averted for a gag when Peppe flings a knife at the door in irritation after Mario quits the gang. The knife bounces off and falls to the ground, and he shrugs.
- Blatant Burglar: Capannelle. Peppe bluntly tells him he's too conspicuous, wearing "a thief's uniform" (he's dressed like a jockey, which stands out).
- The Caper: A plot to rob the safe in a pawn shop. But it's a comedy, played for laughs, unlike deadly serious takes on The Caper from this era like Rififi.
- Chekhov's Gun: Mario's habit of imitating Michele's voice when coming to see Michele's sister Carmelina. This leads to Carmelina mistaking her brother for Mario when Michele comes home, leading Michele to figure out his sister is dating Mario, and getting very angry.
- Conversation Cut: Peppe explaining the plan to the others in the attic of an apartment building cuts smoothly to Peppe on the scene explaining the plan as the gang cases the neighborhood.
- Curtain Camouflage: Carmelina hides Peppe behind a curtain when her brother and the man he's picked to marry her show up.
- Follow That Car: Parodied when Cosimo, who has just gotten out of prison, follows Peppe to the amusement park and does this with bumper cars.
- Mentor Archetype: Dante Cruciani, played by Totò; a retired burglar, still very knowledgeable about both thieving and not getting caught.
- My Sister Is Off-Limits!: Michele flies into a violent rage when he finds out that Mario has been making time with Carmelina.
- Plethora of Mistakes: The vacant apartment turns out to actually be occupied (although they find a way around that). One of the gang plunges into a vat of sewage in the basement. Another nearly falls through the skylight. Capannelle's first attempt to drill through the thin stucco wall results in him hitting a water pipe. Then when they finally break down the wall they break down the wrong wall, knocking a hole into the apartment's kitchen rather than the adjoining pawn shop. Finally, having run out of time to rob the pawn shop, they stop to have noodles for breakfast in kitchen—and they manage to blow up the stove.
- "Shaggy Dog" Story: The last shot about sums it up: a closeup of a newspaper article about an unknown person or persons who climbed in the window of an apartment, broke down a wall and ate some pasta.
- Stupid Crooks: They're all idiots, really. Cosimo gets arrested when he tries to steal a car and averts Hassle-Free Hotwire, setting off the car alarm instead. As they're attempting the heist they spill all their tools because they forgot to lock the suitcase. They utterly bungle the heist (see Plethora of Mistakes above).Tiberio (to Peppe): Stop thinking. That's the best thing you can do for yourself.
- Title Drop: In Italian, at the very end via a newspaper headline. "I SOLITI IGNOTI: Col sistema del buco rubano pasta e ceci." ("Persons unknown bore hole to steal pasta and beans.")
- What You Are in the Dark: Peppe manages to get the keys to the apartment from Nicoletta, the gorgeous maid. But he's fallen in love with her and he can't bring himself to implicate her, so he doesn't tell the others he has the keys, forcing them to make a difficult, time-consuming break-in.
- Wretched Hive: Rome. The gang ask a boy for directions...Capannelle: Do you know a guy called Mario who lives around here?
Boy: There are a hundred people named Mario here
Capannelle: Yeah, but this one's a thief...
Boy: Still a hundred.