The stowaways are still hungry, so they wander on deck looking for food to eat. They find a long buffet spread where Tomasso becomes bug-eyed while viewing all the sumptuous dishes available. Their plates are loaded up with Italian food. After dinner, there is a large production number - Riccardo sings "Cosi-Cosa," Fiorello solos on the piano with tricky fingerwork and amuses his audience of children. As Tomasso plays the piano, he slams the piano top down on his hands to make them go limp. He also treats everyone to a harp solo, a beautiful rendition-reprise of the film's hit song: "Alone."

Lassparri spots the stowaways and notifies police, who pursue them, catch them, and hold them in the brig - the "Detention Cabin." After Fiorello grows tired of listening to Tomasso play "Cosi-Cosa" on a kazoo, he tosses it out a porthole, and Tomasso jumps into the ocean after it. From another porthole, Driftwood gives him a rope for a lifeline. Tomasso ends up being swung into the porthole and cabin of three sleeping, bearded Russian aviators.

With a devilish and mischievous gleam in his eyes, Tomasso picks up a pair of scissors to cut their whiskers off to use them as bearded disguises. As he reaches for the first beard and lifts the tuft of hair up, an animated butterfly flutters out. He snaps the scissors at the white-winged creature that attempts to fly away unharmed.

The three stowaways, now masquerading as Russian aviators with glued-on beards, are escorted from the ship with their manager/interpreter Driftwood, who wants to cut through all the pompous ceremony. He rips up the welcoming committee's speech:

Here, give me that. Let's cut this short. The whole thing is very simple. They want you to go to the City Hall and the mayor's gonna make another speech. We can tear up the mayor's speech when we get there.

The strange aviators ("distinguished visitors") are given the mayor of New York City's official ticker-tape parade and taken to a public ceremony and welcome at City Hall. (Their greeting sign reads: Welcome to the Heroes of the Air.) In the classic City Hall scene before thousands in the Manhattan crowd, Fiorello is asked to speak about their achievement. He nervously asks Driftwood how to bluff his way through:

Fiorello: What'll I say?
Driftwood: Tell 'em you're not here.
Fiorello: Suppose they don't believe me?
Driftwood: They'll believe you when you start talking.

Fiorello delivers a non-sensical speech about the aviators' trouble-ridden trip to America, one in which they repeatedly ran out of gas halfway across the ocean:

Friends...how we happened to come to America is a great story. But I don't tell that. When we first started out, we got-a no idea you give us this-a grand reception. We donna deserve it. And when I say we donna deserve it, believe me, I know what I'm a-talkin' about...So now I tell you how we fly to America. The first time we started, we get-a halfway across when we run out-a gasoline and we gotta go back. Then I take-a twice as much gasoline. This time we-a just about to land - maybe three feet - when whaddya think? We run out-a gasoline again and a-back we go again to get-a more gas. This time I take-a plenty gas. Well, we get-a halfway over when what-a you think-a happened? We forgot-a the aeroplane. So we gotta sit down and we talk it over. Then I get-a a great idea. We no take-a gasoline. We no take-a the aeroplane. We take a steamship. And that, friends, is how we fly across the ocean.

The audience has no hint of suspicion about the aviators, even after the preposterous speech. Tomasso, another hero, is called up next to present his memoirs and exploits. To stall for time, he pours a glass of water from a pitcher and drinks it down. Then, to hold out a little longer, he pours another glass of water and drinks that down too. Driftwood jokes about the numerous glasses of water:

Well, we're all right as long as the water supply holds out...You know, they may have to build a dam in back of him.

When Tomasso's bearded disguise begins to deteriorate (it becomes unhinged when he gets water on his beard and then comes off entirely), Detective Henderson (Robert Emmet O'Connor) in the crowd recognizes that they're imposters. The aviators pretend to be insulted by the charges, so the detective is forced to be quiet:

Henderson: Hey, I think these fellows are phonies!
Driftwood: What's that you say?
Henderson: You heard me.
Driftwood: (In an unintelligible dialect with the aviators) Did you hear what he said? He said you boys are imposters and you absolutely don't belong here at all.
Fiorello: Did he say that about us? I've never been so insulted!
Driftwood (to the Mayor): Do you hear what they say? They say they've never been so insulted in their life and they absolutely refuse to stay here!
Mayor: No, no, please. (Gesturing toward Henderson) He didn't mean it. (Gesturing toward the aviators) Tell them he didn't mean it.
Driftwood: (More dialect with the aviators) (To Henderson) Of course, you know this means war!
Mayor (to Henderson): Now see what you've done!

For his offense, the detective apologizes to Tomasso - the only aviator left on the stage, who is now drinking directly from the almost-empty pitcher. Tomasso kisses Henderson Russian-style on both cheeks, thereby transferring his beard to the detective's face. Henderson realizes he has been duped - Tomasso must flee and disappear under the grandstand.

The stowaways end up hiding out in Driftwood's hotel room, where cots have been set up to accommodate the three stowaways. The next morning when the alarm clock rings on one of the empty cots, Tomasso smashes it with a large mallet. They sit down to a large breakfast - in a pantomime scene,Tomasso ravishes the breakfast table by eating a "cupcake" of one china cup between two hotcakes, Driftwood's cigar in a pancake roll, and part of Fiorello's necktie on another hotcake:

Fiorello: I'm glad I didn't bring my vest.
Driftwood: I forgot to tell you. He ate your vest last night for dessert.
Fiorello: He's half goat.

Tomasso then wears his breakfast. He uses the top of the sugar bowl as a mirror and applies sugary "pancake" makeup with a pancake, lipstick from a ketchup bottle with his little finger, and dabs of sauce as perfume behind his ears.

Ominous knocks are heard at the door. The stowaways hide on the fire escape as plainclothesman detective Henderson, the symbol of law and order, enters:

Henderson: You remember me. I'm Henderson, plain-clothesman.
Driftwood: You look more like an old-clothes man to me.
Henderson (quickly glancing around): Nice place.
Driftwood: Well, it's comfortable.
Henderson: You live here all alone?
Driftwood: Yes. Just me and my memories. I'm practically a hermit.
Henderson (suspiciously): Oh! A hermit! I notice the table is set for four.
Driftwood: That's nothing. My alarm clock is set for eight. That doesn't prove a thing.
Henderson: A wise guy. Well, I'll take a little look around.

In a hilarious bed-switching sketch, a classic in-and-out-of-doors scene, Henderson is led around by Driftwood for an inspection of the premises, as the stowaways stay just out of his sight. Driftwood conducts a tour through his small two-room apartment for the snooping detective, searching for the stowaways. In the bedroom, there are four beds. Henderson asks the obvious question:

Henderson: What's a hermit doing with four beds?
Driftwood: Well, you see those first three beds?
Henderson: Yes.
Driftwood: Last night I counted five thousand sheep in those three beds, so I had to have another bed to sleep in. You wouldn't want me to sleep with the sheep, would you?

As they move back and forth between the two rooms (the living room and the bedroom), the stowaways hide on the fire escape, and then move the furniture (one bed at a time) from the bedroom to the living room while Driftwood keeps the detective distracted. The stowaways furtively reduce the number of beds in the bedroom - first to three, then two, then one, and then to none. Henderson is totally disoriented as he staggers from "room" to "room" by way of the fire escape:

Henderson: Who are you talking to?
Driftwood: I was talking to myself, and there's nothing you can do about it, I've had three of the best doctors in the East.
Henderson: Well, I certainly heard somebody say something.
Driftwood: Oh, it's sheer folly on your part.
Henderson: What's this?
Driftwood: Why, that's a fire escape. And, uh, that's a table, and this is a room, and there's the door leading out, and I wish you'd use it, I...I vant to be alone!
Henderson: You'll be alone when I throw you in jail.
Driftwood: Isn't there a song like that, Henderson?...
Henderson: (He enters the bedroom - by way of the fire escape - from the living room) What became of that fourth bed?
Driftwood: What are you referring to, Colonel?
Henderson: The last time I was in this room, there were four beds here!
Driftwood: Please! I'm not interested in your private life, Henderson.
Henderson: Oh-h-h. (He barges into the living room) Say! What's that bed doing here?
Driftwood: I don't see it doing anything.
Henderson: There's something funny goin' on around here, but I'll get to the bottom of it. (He walks out to the fire escape and comes around into the bedroom a second time) Hey, you!
Driftwood: Coming!
Henderson: Am I crazy, or are there only two beds here?
Driftwood: Now, which question do you want me to answer first, Henderson?

When the detective goes into the bedroom directly behind him, the bedroom door turns into another bed. His next visit to the bedroom finds it completely bedless, and he begins to believe he's going crazy. Finally, the detective comes around the fire escape to the living room (which now has all the beds). He runs around the fire escape into the bedroom, where he sees two bizarre cloaked figures - an old lady knitting (Tomasso) with a tea doily on her head, and rocking in an armchair (Fiorello under a sheet masquerading as a chair). Across from her is another man (Driftwood) with a fake beard, reading a newspaper and smoking a cigar. Thinking he has wandered into the wrong apartment ("Oh I beg your pardon, I must be in the wrong room"), the detective leaves confused and apologetic, ending his hopeless search.

The opening night of the opera finally arrives. Driftwood is warmly greeted backstage by the chorus: "Good evening, Mr. Driftwood," and by the elevator man: "Waiting for you, Mr. Driftwood. Step right in," but upstairs, he finds his name being scraped off his office's door. In Gottlieb's office, Driftwood realizes he's been fired: "Mrs. Claypool has decided to dispense with your services immediately." Managing Director Gottlieb has become Mrs. Claypool's new business manager. She has been convinced to fire him for being a fraud and for associating with "riffraff." Driftwood protests and demands his salary:

Gottlieb: I find that you have overdrawn your salary for the next six months.
Driftwood: Well, in that case, I'll take one week's salary.
Gottlieb: You'll take nothing. Get out.
Driftwood: Well, if that's your best offer, I'll get out. But I'm not making a nickel on it.

In a final gesture, he withdraws his offer of marriage to Mrs. Claypool. Disgruntled, he slams the door and strides to the elevator: "Thanks I get for working my fingers to the bone." The positive greetings he received upon his arrival are harshly turned negative. He is kicked down four flights of stairs by the elevator man, and then tossed out the door onto the street.

The stowaways and out-of-work Driftwood retreat to the park where there's no room on a cold bench for all four of them. Driftwood is ordered off the grass next to the bench by a passing cop. Even the water fountain dries up when he tries to take a drink. Fiorello says: "I'd give you my seat but I'm sitting here." News arrives when Rosa joins them - that she has been banned from singing and fired from the opera company - at Lassparri's request - because she spurned the egotistical singer. Driftwood concocts a plan of revenge that will accomplish three things:

• humiliate opera director Gottlieb
• target Lassparri, kidnap him, and replace him with Riccardo
• and reinstate Rosa (put Riccardo and Rosa in the lead roles)

When Gottlieb returns to his office that evening, Driftwood is sitting in his chair, and Tomasso is pouring drinks with his feet for the stowaways. When Gottlieb objects and attempts to phone the police to have them arrested, Tomasso strikes the Managing Director on the head, leaving him unconscious (and locked up in the closet, stripped of his clothing).

Driftwood takes over as Managing Director, and joins Mrs. Claypool in Gottlieb's opera box for the opera's opening night. Driftwood delivers the address Gottlieb was expected to give before the curtain goes up - he audaciously introduces the opera season from the opera box:

Ladies and Gentlemen. I guess that takes in most of you. This is the opening of a new opera season, a season made possible by the generous checks of Mrs. Claypool. (Applause) I am sure the familiar strains of Verdi's music will come back to you tonight, and Mrs. Claypool's checks will probably come back in the morning. Tonight marks the American debut of Rodolfo Lassparri. (Applause) Senor Lassparri comes from a very famous family. His mother was a well known bass singer. And his father was the first man to stuff spaghetti with bicarbonate of soda, thus causing and curing indigestion at the same time. And now on with the opera. Let joy be unconfined. Let there be dancing in the streets, drinking in the saloons and necking in the parlor.

In the film's spectacular final sequence, the completely chaotic performance of Verdi's Il Trovatore opera ("a night at the opera") is a deliberately assaultive satire on the operatic form. Fiorello and Tomasso have joined the orchestra as conductors. Tomasso plays his trombone with a violin bow, and he fences with the conductor before the overture. In the meantime, Gottlieb, who has revived and escaped from the closet (wearing Driftwood's ill-fitting clothing), arrives at his opera box and forces Driftwood to flee. Gottlieb also stomps around backstage trying to locate Fiorello, Tomasso, and Driftwood, but nobody knows anything, making him even angrier and more exasperated.

The orchestra's sheet music has been changed, so when they turn to page two of the overture, they begin playing "Take Me Out To The Ball Game." A baseball game is simulated in the orchestra pit - Tomasso swings in the batter's box with a violin as Fiorello pitches, and Driftwood is seen hawking peanuts up and down the aisles in ballpark style, yelling "Peanuts, Peanuts."

When the curtain finally goes up after the orchestra's overture, a gypsy woman is singing on stage. Driftwood, back in one of the opera boxes, curses her with: "Boogie, boogie, boogie. How would you like to feel the way she looks?" Gottlieb hears Driftwood's voice and sends his men after him. Fiorello and Tomasso emerge on stage dressed as gypsy peasants. Tomasso throws the gypsy woman a funny face. Gottlieb has notified the police - Henderson and the cops arrive on the scene - backstage. When the gypsy hits a high note, Driftwood asks:

What was that? High C or Vitamin D?

More havoc ensues - thinking that Gottlieb is Driftwood, Henderson strikes him on the head with a heavy cast-iron frying pan. Simultaneously, Henderson is knocked out by Tomasso. Gypsy-costumed Tomasso grabs a whip, strips off a dancer's costume as she performs, whistles and waves at the audience from the stage, escapes from Gottlieb and Henderson (dressed as gypsies) closing in from the wings by climbing up the scenery backcloth, and then swings Tarzan ape-like across the stage on one of the ropes that control the backdrops.

As Lassparri sings center-stage, he finds himself performing in front and in back of moving and changing backdrops controlled by the ropes Tomasso is swinging on. The rapid succession of inappropriate backdrops changes from the ends of two railroad cars in a railroad yard depot, to a fruit stand cart, to a battleship. Tomasso performs trapeze-like, gymnastic acts on top of and through the backdrops, rips through one all the way to the floor, and then clambers back up (!) the backdrop to escape police.

When the theatre goes pitch-black, Lassparri is kidnapped by Tomasso and Fiorello and carried up to the roof of the stage. Gottlieb demands a tenor to satisfy the audience - he begs Riccardo to fill the role in costume. Riccardo insists that he has been "rehearsing" with Rosa and must sing with her - otherwise, he won't perform. Despairingly, Lassparri watches from above with a gag in his mouth as the crowd adores the sensational two young singers who triumphantly perform arias from "Il Trovatore" and "Pagliacci" - the opera continues on a more sane note. When Lassparri struggles free and the culprits are arrested, he returns to the stage for an encore, but he is booed and fruit is thrown at him by the audience:

Lassparri: (complaining) Never in my life have I received such treatment! They threw an apple at me!
Driftwood: Well, watermelons are out of season.

Riccardo forces Gottlieb to reinstate Driftwood and negotiate new contracts with Driftwood and Fiorello so that he can sing: "Well, if they're arrested, I ought to be too. I can't sing if I'm arrested." Gottlieb agrees to their terms and signs up the very popular Riccardo and Rosa as the new stars of the opera company. He also promises that police charges will be dropped against all of them. Rosa and Riccardo return to the stage, singing. The mad, contrived antics of Driftwood, Fiorello, and Tomasso have triumphantly succeeded - the young romantic couple finds happiness and the film's plot is satisfyingly fulfilled.

In the last image, Fiorello and Driftwood continue to argue over the "party of the tenth part" in the new contract, while Tomasso playfully splits the back of Gottlieb's evening coat.