In the film's highlight scene, the villainous usurpers send a slinky call girl, big beautiful blonde Miss Nora "Flo" Marlowe (Esther Muir) to Hackenbush for a dinner date. The conspiratorial plan is to seduce him in order to further discredit him in the eyes of Mrs. Upjohn. Stuffy has overheard the plan. Tony plays a pantomime game with him to guess and piece together what he has heard. His misinterpretation, including the following key words, is priceless:

Hackenbush (Stuffy outlines a large mustache, imitates the famous Groucho crouching walk, and then hacks at a bush or hedge: "Hack-a-bush")
A woman (an undulating shape that is not a snake or an apple dumpling)
A knock on the door (not a wooden leg, woodpecker, or a headache)
A frame job (a park sign's frame).

Tony and Stuffy decide to save him from the "frame" up.

Hackenbush preens for the date, dances around to a Strauss waltz, smells the flowers on the table, sprays perfume around, and shows tremendous anxiety before his date Flo arrives at his door:

Flo: Oh doctor. Thank you.
Hackenbush: Thank yu. (One of many thank yus.) Do you like gardenias?
Flo: I adore them. How did you know?
Hackenbush: I didn't, so I got you forget-me-nots. One whiff of this and you'll forget everything.
(He hands her a wilted sunflower. He seats her and pushes in her chair at the table.)
Flo: Thank you.
Hackenbush: Thank yu.
Flo (handing him her wrap): Do you mind?
Hackenbush (taking her stole wrap): Not at all. I always take the wrap.

Hackenbush can't see her over the large centerpiece on the table. Just as they are settling in for a little seduction - and a betrayal of Mrs. Upjohn, Tony and Stuffy arrive to interrupt the romance and save him. Tony pounces on Flo himself, leaping onto her lap. Stuffy jumps on too, and then invites Hackenbush to join them. He replies: "Not for me, three men on a horse." His friends warn:

Tony: She's in with Whitmore. She's trying to frame you.
Flo (insulted): Why, I've never been so insulted in my life!
Hackenbush (after looking at his watch): Well, it's early yet.

They get into a tugging match, pulling on one of her arms to take her out (and ripping her stole) as Hackenbush pulls her other arm to keep her there. Flo puts on powder makeup, and orders Stuffy: "Scram. Blow." He blows and she is instantly covered with a cloud of white face powder. Hackenbush throws his friends out. He falls off his own chair because he can't keep his eyes off her.

Flo: How about a little Scotch?
Hackenbush (holding out his glass expectantly): Why, I'd love it!...Oh, I'll ring for some...

Tony returns, disguised with a hotel detective's mustache:

Tony: Have you got a woman in here?
Hackenbush: If I haven't, I've wasted thirty minutes of valuable time.

Tony blows his whistle for his assistant Stuffy, who enters with two bulldogs on leashes. Stuffy immediately directs his magnifying glass to Flo's back. Hackenbush tells him: "If you're looking for my fingerprints, you're a little early." After putting a piece of dinner meat in the detective's pocket, and causing the dogs to race around the room, Tony and Stuffy are dragged out the door, leaving them alone once more.

Hackenbush asks: "Tomato soup? Have you got a can opener." Flo replies that she isn't hungry, and only wants to snuggle close to him. In a classic line of dialogue, she asks:

Flo: I want to be near you. I want you to hold me. Hold me closer! Closer! Closer!
Hackenbush: If I hold you any closer, I'll be in back of ya!

They go to sit on the couch, and his rescuers enter the room a third time, carrying wallpapering tools and materials:

Tony: We come to hang the paper.
Hackenbush: How about hanging yourself instead?

In an incredibly hilarious sequence, the Wallpapering to the Wall scene, they redecorate the room, plastering and wallpaper both of them to the wall while they sit on the couch.

Suddenly, Whitmore and Mrs. Upjohn enter the room. Hackenbush bursts through the wallpaper to explain to Mrs. Upjohn that he is having the room wallpapered for their honeymoon suite. Whitmore is exasperated for having been fooled. After they have left, Flo emerges screaming from under the couch pillows where she has been pinned and crushed:

Flo: I'll get even. You, you dirty, low-down, cheap, double crossing snake.
Hackenbush: Thank yu.

Stuffy wallpapers her rear end as she storms out of the room.

The next day, Mrs. Upjohn apologizes to Dr. Hackenbush for mistrusting him. He suggests that paying the notes on the sanitarium for Judy would help to make up for it. Hackenbush flatters Mrs. Upjohn, professing his love for her, adding an oft-quoted line:

It's the old, old story. Boy meets girl - Romeo and Juliet - Minneapolis and St. Paul!

Meanwhile, Whitmore has called on Austrian specialist Dr. Leopold X. Steinberg (Siegfried Rumann) to critically observe Hackenbush. Steinberg doesn't believe in his diagnosis of Mrs. Upjohn: double blood pressure. But Mrs. Upjohn is pleased with Hackenbush's diagnosis:

Mrs. Upjohn: Dr. Hackenbush tells me I'm the only case in history. I have high blood pressure on my right side and low blood pressure on my left side.
Steinberg: There is no such thing. She looks as healthy as any woman I ever met.
Hackenbush: You don't look like as though you ever met a healthy woman.

To settle their dispute, a medical examination of Mrs. Upjohn is proposed. Hackenbush is scared to death of the prospect - he will be seen as a fraud and Mrs. Upjohn will be declared healthy. He scurries around to pack and depart:

Gil: Are you a man or a mouse?
Hackenbush: You put a piece of cheese down there and you'll find out.

In the end, however, he is convinced to stay to save the sanitarium for Judy.

Preparing for the exam, Hackenbush repeatedly washes his hands in the operating room. He deliberately drops his watch in the water rather than leave it on the counter near Steinberg who might steal it:

I'd rather have it rusty than missing.

His two assistants Stuffy and Tony enter with white uniforms inscribed: "JOE'S SERVICE STATION" and "BRAKES RELINED."

Confusion abounds - Tony and Stuffy take Dr. Steinberg's name as their own. Hackenbush introduces the many Steinbergs to each other, and they all bow simultaneously:

Dr. Steinberg, by a strange coincidence, this is another Dr. Steinberg. May I...introduce my colleagues and good friends, another Dr. Steinberg. This is a Dr. Steinberg, that's a Steinberg. Dr. Steinberg and (pointing to Mrs. Upjohn) a Mrs. Steinberg.

Then Hackenbush points to an anatomical drawing and continues the masquerade:

And Doctor, I'd like you to meet another Dr. Steinberg. (Hackenbush points to a second identical drawing.) That's Steinberg junior.

The real Dr. Steinberg is furious and complains:

Dr. Steinberg: In all my years of medicine - .
Hackenbush: Don't point that beard at me! It might go off.

Stuffy is ordered to take Mrs. Upjohn's pulse, and he snatches her purse off her lap, because he can't spell. They need to resterilize their hands, so they again wash their hands, singing "Down By the Old Mill Stream." This is repeated again to kill time. They ask for new coats, and three nurses bring them in. Stepping into one with arms out, Stuffy grabs one of the nurses. Hackenbush cautions: "Just put the gown on, not the nurse." He whisks the nurse's outer garments off, leaving her in a slip. Steinberg questions their insane, ridiculous medical examination methods, but Hackenbush strikes back: "Yes, that's what they said about Pasteur!"

Mrs. Upjohn is laid out and strapped into a tilted-up operating chair/table. A "MEN AT WORK" sign is hung at her feet. She is prepared as if in a barber's shop - lathered and shaved by Tony. Her shoes are polished by Hackenbush and she is manicured by Stuffy. She is bounced up and down in the operating chair. X-rays are called for. Stuffy pantomimes selling an armload of newspapers as Hackenbush impersonates a newsboy: "Ex ray (Extra), ex ray (extra)." And then Stuffy sets off the room's overhead sprinkler system, dowsing the entire operating room with rain. Gil's racing horse Hi-Hat charges through the room and rescues the "Hackenbush team" of doctors before they are apprehended.

Despairing with Gil in a barn, they dry themselves around a fire. Hackenbush wants to take all the blame, but becomes angry when Tony agrees to let him. Judy arrives with blankets in her arms to keep them warm. She tells them that by the next day, the sanitarium will belong to Morgan. To cheer her up, Gil sings the hopeful "Tomorrow Is Another Day."

A Pied-Piper-like Stuffy leads a cavalcade of children through the barn in "Gabriel" ("Who Dat Man?"), a musical number that has little connection to the film's main plot. That leads to another exuberant song and jitterbug-dance number through Negro shanty towns, titled "All God's Children Got Rhythm." [Note: This was the only Marx Brothers film to receive a competitive Oscar nomination -- Dave Gould's Best Dance Direction for this song/dance number.]

[Mostly uncredited performers: Jazz singer Ivie (Ivy) Anderson (who was singing with Duke Ellington's band at the time) and the Crinoline Choir performed the gospel song. The gravity-defying, jitter-bugging number was danced by Herbert "Whitey" White's Lindy Hoppers - White was the undisputed king of the Lindy Hop (the original swing dance), and his dancers were originally from the Savoy Ballroom in Harlem. The number was choreographed by Frankie Manning. Dorothy Dandridge was also an uncredited performer in the 'All God's Children Got Rhythm' number.]

The music is interrupted by the sheriff and Morgan, who have come to seize Hi-Hat. The Marx Brothers appear in black-face and mingle with the crowd to escape detection, but their ploy isn't effective. The horse becomes agitated when he hears Morgan's voice. With Stuffy riding him, the horse leaps over the barn door to avoid capture. His jump brings to light the fact that he is a born jumper (and not a race horse), and a possible contender in Saturday's steeplechase race.

In the final slapstick sequence at the Sparkling Springs Racetrack, Gil enters Hi-Hat in the Grand Steeplechase. The horse is smuggled into the race past Morgan's men in an ambulance, but the horse is discovered. To delay the start of the race, Stuffy puts slippery harness soap under the saddles of all the riders, and Stuffy and Tony blow the spectator's hats onto the track. Cars looking for parking are directed onto the race track. The race finally gets under way, but is delayed again when the pranksters reroute the course into the countryside. The delays allow time to retrieve Hi-Hat and smuggle him back into the race.

Stuffy rides Hi-Hat as jockey. Hi-Hat balks at the first jump, but Stuffy has a solution to get him running - he shows Hi-Hat a picture of the hated Morgan, and the horse takes off. The sound of Morgan's voice is projected over the loudspeakers to also spur him on. Stuffy rides Hi-Hat to defeat - but then it is discovered that Hi-Hat and Morgan's horse Small Wonder were switched when they were upset in one of the jumps. Morgan's jockey rode Hi-Hat to victory.

Hi-Hat wins the $50,000 purse, to be used to save the sanitarium, and Gil wins his love Judy. In the celebration while singing the song "Tomorrow is Another Day" and parading along, Hackenbush delivers the film's punchline, promising marriage to Mrs. Upjohn:

Emily, I have a little confession to make. I really am a horse doctor. But marry me, and I'll never look at any other horse.