Francis Bigger (Frankie Howerd) is a charlatan faith healer, convinced that "mind over matter" is more effective than medical treatment. During a lecture, he stumbles offstage and is admitted to the local hospital. In hospital, he incessantly groans and whines about being "maltreated", demanding better treatment than the other, eccentric patients. These include: bedridden layabout Charlie Roper (Sid James) who shams illnesses to stay in hospital; Ken Biddle (Bernard Bresslaw) who makes frequent trips to the ladies' ward to flirt with his love interest, Mavis Winkle (Dilys Laye); and Mr Barron (Charles Hawtrey) who seems to be suffering sympathy pains while his wife awaits the birth of their baby. While being treated, Bigger meets two very different doctors. Clumsy yet charming Dr. Kilmore (Jim Dale) is popular with the patients and loved from afar by the beautiful Nurse Clark (Anita Harris) while hospital registrar Dr Tinkle (Kenneth Williams) is universally detested, as is his battleaxe Matron (Hattie Jacques), who harbours an unrequited love for him.
After Bigger's arrival, novice nurse Sandra May (Barbara Windsor), arrives at the hospital with her intention to declare her (questionable) love for Tinkle, and enters his room, violating hospital rules that female staff are not permitted in the male quarters. Matron and Kilmore burst in on her declarations of love, which are cruelly rebuffed by Tinkle. Matron throws Nurse May out, and she leaves while tearfully announcing she'd rather die than live without Tinkle. Dr Tinkle fears for his position after this incident, and contrives with Matron to get rid of Kilmore and Sandra May, lest they reveal the truth.
Shortly after, Sandra May climbs on to the roof of the nurses' home to sunbathe in her bikini top. Dr Kilmore and Nurse Clark assume she is going to throw herself off the roof in despair after Tinkle's rejection. Kilmore rushes to save her and climbs on to the roof. He realises she is sunbathing and prepares to leave, but Sandra assumes to her horror he is leering over her, and shrieks in fear. Her screams attract attention and soon the entire hospital staff and townspeople flock to watch. Nurse Clark attempts to help Kilmore before he falls off, but he accidentally tears her skirt off, leaving her in her underwear and stockings. Kilmore crashes through a window to safety, but lands in a bath ... with a nurse in it, who assumes he is attacking her. His good reputation is destroyed among everyone except his patients.
Dr Kilmore is given a hearing with the hospital governor, but Matron and Tinkle deny his revelation of Sandra May's fight with Tinkle. As Sandra May has left the hospital, Kilmore has no proof to support him and is forced to resign. Nurse Clark reports the treachery of Tinkle and Matron to the patients and together they decide to exact revenge upon the pair for what they have done.The patients stage a nocturnal mutiny - their first victim is Sister Hoggett (June Jago), whom the female patients overpower and leave bound and gagged in a linen cupboard, incapacitating her from alerting the orderlies. The male patients take care of Tinkle while the females take care of Matron. The ladies manage to get Matron to confess by torturing her with a towel bath, while the men get Tinkle to confess by performing an enema on him, since their previous attempt to do so by giving him an icy cold bath failed. The next day, Dr Kilmore is appointed the new hospital registrar while Tinkle is reduced to a simple doctor. Mr Barron, now fully recovered and cured, and his wife finally have their baby, and Bigger and his newly wedded wife Chloë Gibson (Joan Sims) bicker as they leave the hospital. However, on their way out, Bigger deliberately falls on the steps and injures his back again to avoid anymore difficulties with his wife and is brought back to the hospital.
- Sidney James spent most of his screen time in bed, as he had recently suffered a heart attack.
- Contains a sly reference to Carry On Nurse (1959), specifically the daffodil thermometer scene. When a nurse approaches Francis Bigger with a daffodil, he says, "Oh no you don't! I saw that film!"
- Producer Peter Rogers had to give his wife, Betty E. Box, producer of the "Doctor" series of films, a percentage of the takings, for the use of the "Doctor" title.
- Kenneth Williams originally turned down the role of Dr Tinkle and was given Francis Bigger, but found fault with the role and returned to the Tinkle character.
- Joan Sims was offered to be Matron, but she claimed that Hattie Jacques was the best Matron, after playing one in Carry On Nurse (1959).
- There were rumours that this would've been the last Carry On, as Don't Lose Your Head(1967) and Carry On... Follow That Camel (1967) had made the least money in the series at the time. It's probably why many familiar faces reappear that haven't been in the series for at least 3 years or more.
- The film was the third biggest general release hit at the British box office in 1968.
- This probably would've been the last time that any special guests would appear in the series, since Phil Silvers failed to draw in audiences for Carry On... Follow That Camel(1967), but Frankie Howerd's performance managed to gain the series' mojo back.
- Peter Rogers was wary of included two well known camp performers Kenneth Williams and Frankie Howerd in the same cast. Indeed their roles were seemingly interchangeable. Days after turning the film down, Kenneth was told that Frankie was out of the film and was now offered the leading role. Typically, Kenneth balked at accepting the responsibility and rejected the idea, ironically seeking solace in the role of Dr Tinkle, the part he had turned down days before. Although Peter maintained that he kept them apart on screen, in actual fact, Kenneth and Frankie do share a couple of brief scenes together.
- The portrait hanging over one of the door is of James Robertson Justice with the caption "Dr James R. Justice, Founder". This is a reference to the rival "Doctor" series of films, produced by Peter Rogers' wife Betty E. Box, in which Justice starred.
- The actor who plays the mysterious 'Mr Wrigley' is an obvious nod to the Invisible Man, as portrayed by Claude Rains. However, the identity of the actor playing the character in this film has never been known.
- Jim Dale did all his own stunts including the trolley ride down the stairs and through a window. despite a stuntman being on stand by.
- When Mr Bigger is being stretchered through some double doors following his X-Ray, he falls off the trolley onto the floor. In the close-up of an agonized Mr Bigger, you can see the pink uniform of the Nurse who later picks up Mr. Bigger. In the next shot, showing the whole corridor, the Nurse appears after the trolley has been wheeled out of the double doors.
- When the porter goes over to Sid James with the tea he has two cups in his hand. But when we see the porter handing the tea to Sid James he has only one cup in his hand.
- When the ambulance arrives at the hospital, it parks at an angle in relation to the door. In the next shot, it is directly in line with the entrance.
- Nurse May's bikini top is undone while she is sunbathing on the roof of the nurses' home. After she turns over, she sees Dr. Kilmore and stands up screaming while still holding the towel in front of her and her top has been done up again.
- When Mr Roper is asking the nurse if he can have a fag, he is told to take his medicine, so he takes it. But in the next shot, when the nurse has gone and he is holding a newspaper, the medicine has disappeared.
- Mr Bigger's hands change between shots from being under the bed covers to over the bed covers and back again in the scene just after he has dressed in his hospital gown.
- Frankie Howerd as Francis Bigger
- Sidney James as Charlie Roper
- Charles Hawtrey as Mr. Barron
- Kenneth Williams as Dr. Kenneth Tinkle
- Jim Dale as Dr. Jim Kilmore
- Barbara Windsor as Nurse Sandra May
- Joan Sims as Chloë Gibson
- Bernard Bresslaw as Ken Biddle
- Hattie Jacques as Matron
- Anita Harris as Nurse Clarke
- Peter Butterworth as Mr. Smith
- June Jago as Sister Hoggett
- Derek Francis as Sir Edmund Burke
- Dandy Nichols as Mrs. Roper
- Peter Jones as Chaplain
- Deryck Guyler as Mr. Hardcastle
- Gwendolyn Watts as Mrs. Barron
- Dilys Laye as Mavis Winkle
- Peter Gilmore as Henry
- Harry Locke as Sam
- Marianne Stone as Mother
- Jean St. Clair as Mrs. Smith
- Valerie Van Ost as Nurse Parkin
- Julian Orchard as Fred
- Brian Wilde as Man from Cox & Carter
- Lucy Griffiths as Miss Morris - Elderly Patient
- Gertan Klauber as Wash Orderly
- Julian Holloway as Simmons
- Jennifer White as Nurse in Bath (as Jenny White)
- Helen Ford as Nurse
- Gordon Rollings as Night Porter