One of the characters has come down with something. They may be having mysterious fainting spells, or losing time, or too weak to stand, but whatever the symptoms, it's clear it's serious. If the influence of mystical power is implied, you would think they'd have cause to worry and confide in their friends about their suspicions. Or at least wonder why they're sick.
Actually, the more obvious it's not a normal illness, the less likely they'll mention it. Even if your cast includes some of the most helpful doctors or mind readers, the character won't bring it up for quite a few episodes in a row, constantly making the excuse they're just a bit under the weather. This manages to convince their unusually thick friends.
This may be used for one or more Sick Episodes. This may develop into either a Soap Opera Disease or an Incurable Cough of Death. If caused by contact with the bad guys, it may be Allergic to Evil. Often used as an excuse by a Zombie Infectee in denial. Opposite of Mistaken for Dying, where characters assume the worst when it is definitely just a cold.
- In Boku no Hatsukoi wo Kimi ni Sasagu, Kou suffers numerous headaches after the car accident, but he brushes them off saying he's just tired. They're symptoms of brain hemorrhage, that end up making him faint and enter brain death state.
- In Deep Love Ayu believes it's a fever when it clearly isn't. It's AIDS.
- Asa Shigure from SHUFFLE!, who denies there's a problem even as she's intermittently losing consciousness in the hospital. She can easily cure herself with a simple spell, but she doesn't want to hurt her mom's feelings because Ama is an Artificial Human who went through horrible magical experiments in her past. Asa's insistence on not using her magic powers leads to a borderline Super-Power Meltdown, and Rin has to Take a Third Option by stabbing himself to force Asa use her magic on him.
- Watanuki in ×××HOLiC, when his friendship with the ghost woman is making him extremely ill, to the point of coughing up blood, insists that it is "just a cold" even when Doumeki repeatedly asks him if he's sure his symptoms don't have to do with "spirits and stuff".
- In Leafie, a Hen into the Wild Leafie starts exhibiting signs of illness when her son is a teenager. It starts with a sneeze but she ignores it. Hens are not meant to live in marshes. In the end Leafie dies in a Heroic Sacrifice by letting herself be eaten, because she knows she wouldn't survive the winter anyway.
- Child of the Storm: in the sequel, Harry immediately picks out Clark's persistent cold/flu type illness as this, on the grounds that his Healing Factor should give him Perfect Health.
- Royal Business: Spike sees that Pinkie Pie is looking ill. It's actually the long-term effects of being wounded by Red Haze the Dragon in Dragonshyness.
- In Cabin Fever, Marcy discovers some tender red marks on her back while washing her face. There's a flesh eating disease going around, by the way. But Marcy instead seems to believe these marks came from her friend Paul fondling her too vigorously when they recently made love, and even chastises him for this. To add injury to insult, Marcy had (unbeknownst to either of them) just infected Paul with the deadly disease, because she insisted they didn't need a condom because she claimed she was healthy.
- District 9: Wikus is exposed to an unknown black substance in possession of aliens, which causes him to drip black from his nose, vomit black fluid, lose fingernails, and look like he's suffering pneumonia, and shits his pants. He ignores the symptoms because he's trying his best to make a good impression after a recent promotion. He refuses treatment so as not to look weak or incompetent to his superiors.
- In Finding Neverland, Sylvia Llewelyn Davies tries to pass off her illness as a cold, but she doesn't fool her son Peter, who lashes out about being lied to.
- The Killer That Stalked New York (a 1950 film Very Loosely Based on the 1947 New York City smallpox outbreak): Sheila needs to lean against a lamppost to stay upright, but still turns down help from a police officer. She proceeds to nearly faint, so he walks her to the health office next door to see a doctor. She then tries to sneak off before seeing the doctor. Dr. Wood gives her some medicine and instructs her to see her own doctor. Her condition keeps getting worse, but she doesn't seek medical attention until more than a week later, and then only because she had accidentally left her medicine behind when she ran from the police and needed more. She goes back to Dr. Wood, and is shocked when he tells her that she has smallpox, despite the massive vaccination campaign due to the outbreak that she couldn't possibly have missed.
- In [REC], the little girl in the movie isn't infected with latent zombieism... she merely has angina! Honest! Of course, the cast do eventually put two and two together and confront the mother about it, who is bitten to death by her daughter as the infection finally takes hold.
- In Slither, the increasingly deforming marks, welts and swelling caused by infection by the alien worms are invariably "bug bites". Even when the bearers of the bug bites are shambling around like zombies, eating dead neighbors, or turning into amorphous tentacle monsters.
- Annals of the Western Shore: Melle when she's first suffering the effects of the Drum wasting gift in Gifts, but it quickly progresses past her ability to power through the increasing weakness of body.
- In Arrow's Fall of the Heralds of Valdemar series, Herald Dirk claims his respiratory symptoms are this, after weeks of self-destructive behavior including drinking heavily, standing hopelessly outside in the rain, and generally being miserable. He does this for two reasons: he's pining with unrequited love for Herald Talia, whom he mistakenly believes to be in a Love Triangle with his best friend, Kris; and he's trying to cope with the tragic death of a trainee who was under his instruction. The fact that the person who is most suited to help him sort out this mess is Talia, the person he least wants to face in person, compounds the problem, which lasts until he collapses... from pneumonia. The Healers who attend him as he recovers spare no effort in telling him what an idiot he was being.
- In Stephen King's sweeping novel The Stand, events start out with a security systems malfunction in a lab letting an engineered biological weapon to get loose. In the earliest stages, the disease (which would come to be known as Captain Trips) would look just like a cold, with flu, cough, sneezing, sniffles, and stuffy noses. Within a few days, the symptoms would escalate to deadly levels. Many characters think that they caught a cold, and before long...
- Star Wars Legends: Galaxy of Fear: The Planet Plague has Tash, feeling hot and irritable and with a growing rashy lump on her arm, assuming she just has the flu. In fairness her brother has it and she thought she'd just been inoculated with a preventative vaccine for it, and she asked a doctor - but since that doctor had been the one to infect her with The Virus intended to turn her into a Blob Monster, he said it was nothing that wouldn't clear up on its own.
- In 24, the cheater gets a bloody nose. He thinks it's just a bloody nose and, if he tells his anything, he says it's only a bloody nose, but it keeps going. It's the early manifestation of a fatal virus.
- In the Community episode "Epidemiology", a number of guests at the college's Halloween party come down with a mystery ailment whose symptoms include fever and stomachaches. Rich, a doctor, claims the symptoms point to food poisoning which the dean told him to rule out. Then, Star-Burns enters the quarantine area and is grabbed and bitten by the infected Pierce who has a bloodthirsty look on his face. Rich then rules out food poisoning. Though, funnily enough, it technically was food poisoning, caused by infected taco meat the Dean bought from an army surplus store — which, of course, is why he wanted that ruled out. It's just that the symptoms of this type of food poisoning — implied to have been created intentionally as some sort of bioweapon — are less "vomiting and diarrhea" and more "becoming a Technically Living Zombie".
- Doctor Who: After Barbara is poisioned in "Planet of Giants", she initially attempts to write off her symptoms as some sort of minor illness.
- Helix revolves around a CDC team dealing with an outbreak of The Virus at a remote Research, Inc..
- Early in the mission, junior CDC team member Sarah begins to exhibit a hand tremor, which senior scientist Julia incorrectly interprets as a symptom of infection until Sarah tests herself and appears clean. Sarah blames fatigue, and the viewer is likely to attribute it to delayed fear reaction from a particularly trauma-filled day. But in the closing scenes of "274" she pops pills in her quarters, and reveals a large vertical scar on her back.
- Also in "274", after being infected by Patient Zero Peter, Julia herself goes into denial and tells team leader Alan she fainted in the shower due to fatigue, later projecting and thus accusing Sarah of being a Zombie Infectee herself.
- Star Trek:
- In the Star Trek: The Original Series episode "The Deadly Years", Kirk visits sick bay with some aches and pains that he attributes to "muscular strain". Bones scans him and tells him it's an advanced case of arthritis, which turns out to be the first sign of a Rapid Aging affliction.
- In Star Trek: Deep Space Nine's final season, the Founders contract a debilitating disease that affects only them. Odo, who had joined with the disease-ridden Head Founder, kept the fact that the disease was progressing rapidly a secret for several episodes. Bashir synthesizes a cure for the disease, disobeying orders to do so (because it could fall into the Founders' hands). Ironically, it was the friendly offer of this cure to the Founders that ended the Dominion War.
- Played with in that at least one character figures out how sick he is, but doesn't mention it because there is no cure and she knows that he prefers to keep such things private.
- Parodied in That Mitchell and Webb Look with a increasingly ill-looking man with a severe cough who insists it's just that (while sad music plays in the background). Until one day his love interest shows up at the train station to meet him and he's not there. Then he shows up looking perfectly fine. The Edwardian costume drama film it's supposed to be from is called The Man Who Has a Cough and It's Just a Cough and He's Fine.
Woman: Look, I thought you had TB!
Man: TB? No, I'd have mentioned that. God! No, it's just a cough.
Woman: Right... wish I hadn't let you do me now.
- In The West Wing, when President Bartlet collapses in the Oval Office, the First Lady (who is a doctor) immediately cuts her trip short and flies back to DC. She insists that he just has the flu and a high fever. As Leo points out, "[You came back] because the President has a temperature. The President's not in nursery school." She then confesses that the President secretly has multiple sclerosis.
- In Deltarune, Rudolph is hospitalized, and is implied to have been there for awhile. He tells Kris he's just in for some tests because the doctor found "some crap," but insists it's nothing to worry about. However, it's heavily implied that it very much is something to worry about, and he knows it, but he's downplaying how serious it is, at least while talking to Kris and Noelle (both of whom are kids, the latter of whom is his daughter).
- Tracer Tong in Deus Ex develops a cough, but otherwise doesn't make too much mention of it until X51.
- In Disgaea 3: Absence of Justice, Almaz goes with this excuse when he gets infected by an incurable curse that is slowly killing him. He gets better as long as it's not the bad ending.
- In Dragon Quest IX, the town of Coffinwell is afflicted with a curse that makes many of the townspeople ill. Catarrhina, the wife of the doctor who helps the heroes stop the contagion, frequently coughs and mentions feeling faint though excuses it every time. Naturally, she's the only one who dies from her illness.
- At the end of Persona 3, the gameplay notes that the main character is very tired. He dies a couple of days later.
- Pokémon Conquest has Hanbei use a similar excuse on Hideyoshi when asked why he's coughing up a storm. Kanbei doesn't buy it and for good reasons. His real life counterpart was diagnosed with tuberculosis and died from it.
- Colette in Tales of Symphonia kept her Angel Toxicosis secret for a long portion of the game.
- Repeated by her in a later part of the game where she thinks she slept wrong because her neck and shoulder feel stiff. Turns out her skin is crystalizing into a huge exsphere.
- Trauma Team:
- During a Diagnosis mission, Joshua tries to claim nothing is wrong with him. The nurse is not fooled. Neither is Gabe. Much to Gabe's dismay, he has Wermer's Syndrome.
- In an earlier Diagnosis, Jacob Tillman constantly claims nothing is wrong with him. Unlike Joshua, who eventually admits he's not well, he fights you to the end, claiming that nothing is wrong. Turns out, he has a serious heart condition.
- Shion of Xenosaga insists to the other characters that her fainting spells are just fatigue. It's really symptoms of a condition that comes with coming into contact with U-DO, the same condition that her mother was afflicted with.
- Hanna of Hanna Is Not a Boy's Name has vomited blood, become visibly weak and even passed out cold on his job and still insists he's fine.
- This is subverted with Belkar from The Order of the Stick. After his Mark of Justice is activated, he experiences severe vomiting and can barely walk. Haley is about to ditch him as a liability, when the group crosses the boundary of a memory charm. Now none of them can remember that Belkar activated the Mark of Justice, and his sickness is written off as a bad cold or similar.
- Zigzagged in one episode of Aladdin: The Series. The illness that Genie gets is Definitely Just a Cold, but the problem is, when genies get colds, they can't control their magic. Big problem. So while Jasmine has to watch over a sick genie whose magic threatens to level the city (and in one scene, launches about ten Baleful Polymorphs at her in a row in a fit of sneezing) Aladdin has to find a gemstone that can cure in a forbidden temple guarded by a divine, golden guardian, without Genie's help. (Fortunately, the guardian prefers brainteasers to physical fighting.)
- In the first season of South Park, a Zombie Outbreak is mistaken for a nasty case of Pink Eye by most residents, long after the truth should have been blindingly obvious.
- A month prior to his death, Eazy-E admitted himself to the hospital for what he suspected was a case of asthma. He soon learned he was in the advanced stages of AIDS.
- Lemmy from Motörhead, in his final days, had been ill and had only known himself to have diabetes, until after months and months of checkups and only mere days before his demise, had been finally found to be in an advanced stage of cancer.