When someone wants to come up with a name for a disease and is not at all concerned with medical accuracy, they will often just take a word (or a bunch of words) and slap "itis" at the end of it, thus creating names like "my-head-hurts-itis", "sequelitis", "consolitis", and so on. There's also "osis" suffix that can be used for a similar effect.
In real life, the "-itis" suffix refers to an inflammation of the mentioned body part. Hepatitis is the inflammation of the liver, arthritis is the inflammation of the joints, appendicitis is an inflammation of the appendix, etc. So to say that a body part is inflamed, you just say the medical terminus of said part with "itis" at the end.
- In the episode "Hypno's Naptime", a bunch of children have been hypnotized into thinking that they are Pokemon instead of humans. Brock calls this "Pokemonitis", but the weird thing is that he doesn't say it as though he's coining a phrase for this one instance, but rather as though it's a recognized medical phenomenon.
- This is also used as an insult in the episode "All Fired Up!" when Gary claims that talking to Ash would cause him to catch "loser-itis."
- In an Archie Comics (the newspaper strip, but reprinted in the "Gag Bag" column a comic book), Archie is being examined by the school doctor.
Archie: I think I've got the bug that's going around.Doctor: Yes, I know. It's called "Dodge-an-exam-itis".
- In a commercial for Cheetos Mystery Colors Snacks (a variety of Cheetos that turn your tongue different colors), one hapless man greets a stranger after having eaten a few, prompting her to scream, "That man's tongue! He's got blue-tongue-itis!"
- Animorphs: Marco and Jake are interrupted by people when Marco is almost out of bird morph, so his face has a huge beak but still has thought-speak, so he coaches Jake into telling them it's a condition called beakanoma (a growth in the shape of a beak, and a very tragic disease because it only affects smart and handsome people). Jake transmits most of it to the crowd and they leave, still shuddering at the Facial Horror as Marco finishes demorphing.
- In Harry Potter and the Order of the Phoenix it's mentioned that when students use Fred and George Weasley's illness-faking sweets to get out of class in protest of the new headmaster, they say they're suffering from "Umbridge-itis".
- In Ramona Forever, when Ramona Quimby is waiting for her new sibling's birth she's diagnosed with "siblingitis".
- In The Brady Bunch episode "You Can't Win 'Em All", Cindy passes a school test to become a contestant on a televised children's quiz show. Of course, she acts all stuck up about how smart she is. But when she she is actually on the show, she freezes up, staring catatonically at the TV camera for the duration of the (live) broadcast. Carol thinks that Cindy has "Television-itis".
- Apollo Justice: Ace Attorney: The third case features a fictional disease called "incuritis". The name only makes reference to the fact that it has no cure or treatment save for a single substance, which can be extracted from a Borginian cocoon.
- Moshi Monsters has a disease called "frosty fingeritis" that monsters are susceptible to in cold weather. To prevent and/or cure it, you need to wiggle your fingers.
- Octodad: In Dadliest Catch's hospital-themed bonus level, there is a disease called "Unicornitis", where the afflicted person gains a unicorn horn and the ability to fly. Justified because the level is actually a story being told by Octodad's children.
- The Mysterious Mr. Enter noted several times that this trope is one of his pet peeves, and gets upset whenever some cartoon character uses it in a way that does not fit its real life purpose.
- The Animaniacs episode "De-Zanitized" ended with Yakko Warner diagnosing Dr. Otto Scratchansniff as suffering acute Warner-itis.
- In an episode of Arthur entitled "The Secret About Secrets", D.W. gets a secret that she wants not to tell, and asks for a day off from school (she actually gets one) by saying she is sick, then saying she thinks she has secret-itis. Grandma Thora arrives to babysit her and Kate.
Thora: "Your mother tells me you have a very distinctive ailment."
- The Beetlejuice episode "Generally Hysterical Hospital" had Lydia Deetz getting trapped at a Neitherworld hospital and in danger of undergoing a full body transplant. Beetlejuice saves her by tricking the hospital staff into thinking they've contracted a disease called humanitis from Lydia.
- In the Bugs Bunny cartoon "Hare Tonic", Bugs convinces Elmer that he has the "dread-disease-rabbit-itis".
- In The Crumpets, Granny is diagnosed with "foulmouthitis", one making "a constant stream of insults", in one episode.
- Doc McStuffins frequently uses this trope for any toys with diseases or sicknesses. It's somewhat justified given the target demographic, and that they're modified versions of real life diseases and sicknesses that are fairly accurate to reap life.
- In Futurama an "Eighties Guy" had himself frozen until the 31st century when he developed terminal "bone-itis". He was thawed after the cure was invented, but he never got around to getting cured and at the episode's climax the symptoms suddenly displayed themselves.
- One episode of Hey Arnold! had Helga being sick and, because she reads a book of fictional diseases, thinks she has "monkey-nucleosis" (which will supposedly turn her into a monkey and is incurable). As a result, she spends what is a regular 24-hour flu being Mistaken for Dying.
- In Rugrats, one episode has Angelica trick Chuckie into thinking that he contracted "Rhinoceritis", a rare disease that causes its victim to turn into a rhinoceros.
- The Simpsons episode "Lisa the Iconoclast" had historian Hollis Hurlbut jokingly refer to Lisa's interest in learning about Jebediah Springfield as "Jebeditis". Lisa responds by making a joke about having just gotten over her "Chester A. Arthritis", which results in a brief moment of awkwardness when Hollis misinterprets Lisa as saying she has arthritis.
- In Spongebob Squarepants, we can frequently see this trope be used by supposedly qualified people, such as "head-go-boom-boom-itis" in Squid Baby, or "oral-report-itis" in Oral Report.