You have a character. This character is flat out dumb. He is either a Cloud Cuckoolander, The Ditz, or even stupid to the level of Ralph Wiggum. Every bit of humor you get from this character comes from the unpossibility of him failing English or being clueless about how to open a pickle jar among other things.
However, after a few years you hit a snag. You're starting to run low on jokes regarding his sheer stupidity. You've overused jokes about them forgetting to breathe and now you need something different. After all, variety is the spice of life. How do you change that?
The usual answer is to momentarily give this character the Smart Ball. Completely out of the blue, your ditz spouts out a tidbit of knowledge regarding astrophysics or thermodynamics. Some writers, however, take this act Up to Eleven, by writing an entire episode regarding a character suddenly showing unnatural intelligence.
Obviously after five seasons of being The Ditz, you can't just have him become a master of string theory without someone wondering why he never showed it prior. Something has to cause this rapid change in intelligence level. A blow to the head, a scientific experiment, or alien technology shakes his brain up enough to unlock a level of intellect previous unheard of.
The result of this sudden intelligence often involves the character becoming an ace, solving everyone's problems without batting an eye. He becomes an episode-long, equal-opportunity Deus ex Machina, nothing becomes challenging for him to figure out. But this ace-hood can get to his head, turning him into an Insufferable Genius. This can lead to a case of Achilles in His Tent, the other heroes' life is at risk, but he won't help them (or they won't ask for their help) due to their strained relationship.
Often, a suddenly intelligent character will know stuff they never actually learned without so much as an explanation.
Usually the episode ends with something causing the character to revert to his old ditzy ways. Maybe this danger to the other heroes hit him in the head and locked that intelligence away. Maybe the other heroes purposely tricked him into doing something to lose it. Maybe he realizes what a jerk he became and willingly gives it up in the name of mending broken bridges with his friend. Either way, he's back to being the lovable idiot we're familiar with by the time the credits roll.
- The Spider-Man story "Flowers for Rhino" was a whole-plot reference to "Flowers for Algernon," where Rhino decides that he's had enough of being a laughing stock and undergoes an experimental procedure to make himself smarter. This leads to him easily outwitting Spider-Man, then successfully filing a restraining order against the hero in court, then becoming the leader of New York's criminal enterprises before realizing that Victory Is Boring and finding himself without anything left to accomplish. He ends by giving everything up and having his intelligence boosting procedure reversed, and, just to make certain, makes himself even dumber than he was before. The story is probably not canon.
- The excellent short story "Flowers for Algernon"'s entire plot revolves around a type of operation given to a man with a low IQ (Charlie) who suddenly becomes super-intelligent. Sadly, he finds he has no more friends and is no happier than he was when he was dumb.
- Poul Anderson's 1954 novel "Brain Wave" describes the chaos that follows the Earth finally emerging from a region of space that has the property of dampening down intelligence. Archie Brock, a mentally challenged man working on a farm, soon develops an IQ of genius level. Of course, most of the rest of humanity simultaneously develops superhuman intelligence. Many are not altogether happy about it.
- Our Miss Brooks: The episode "Dress Code Protest" has student athlete Stretch Snodgrass volunteer some good advice to Miss Brooks.
Stretch Snodgrass: I've got an idea, Miss Brooks.
Miss Brooks: Not so loud, it'll get away.
- The Burns and Allen Show: A two-part episode in the last season, has Gracie Allen become a genius after being hypnotized into believing she's the smartest woman in the world.
- This out-of-character behaviour was a great tribute to Gracie Allen's skills as an actress, and perhaps was timely given it was very much near end of her career. Gracie Allen retired a mere six months later, having played her lovable scatterbrained character opposite her husband George Burns, since the days of Vaudeville.
- In an episode of Brazilian series Sai De Baixo, The Ditz accidentally becomes intelligent while trying to fix a broken electrical lamp. Despite the fact she was demanding everyone in her family to call her "Doutora (Doctor) Eugênia", they were actually liking her new self. Then, in another attempt to fix the lamp, she accidentally reverted back to normal. In the epilogue, her husband tried to repeat the process but made himself dumb.
- Charles Gunn when he gets his mystical mind upgrade on Angel. It backfired badly though. Wolfram and Hearts doctor deliberately made it temporary so Gunn would beg for it to be fixed, and the relic he signs for in exchange for fixing it contains an ancient god-like demon that kills Fred.
- DuckTales (1987): Bubba's Big Brainstorm has Gyro provide Bubba the Caveduck with a thinking cap, making him an insufferable genius for the span of one episode.
- In an episode of The Adventures of Jimmy Neutron: Boy Genius, the titular character performs an experiment on Sheen to make him a genius. It's successful, but soon it becomes Gone Horribly Right, as Sheen's intelligence just keeps increasing. Eventually his brain becomes so powerful he masters telekinesis. Jimmy has to try to find a way to zap the intelligence back out of him before he takes over the world.
- Inverted in another episode where he makes himself stupid. He just wanted to make himself of average intelligence for the same reason stupid people who play with the trope want to get back to normal but the machine wasn't properly regulated.
- The Simpsons: After a crayon is dislodged from Homer's brain, he becomes a genius. But when he causes the entire town to turn against him after he causes the nuclear plant to be temporarily shut down. At the end of the episode, he gets Moe to stick a new crayon in his brain, reverting him back to being the old, stupid self.
- Spongebob Squarepants: During a day of horseplaying, Patrick falls down a cliff and suddenly becomes a genius. He alienates his friends, and eventually enlists Spongebob in trying to make him stupid again. Turns out the top of Patrick's head had come off and SpongeBob accidentally replaced it with brain coral.
- Regular Show: Tired of being made fun of for not having a high school diploma, Rigby takes a smart drink that makes him a super genius. Mordecai drinks it too and engages in a Escalating War to see who is smarter. Eventually they get so smart that everyone else is too dumb for them to comprehend them, and they have to find a way of dumbing down to normal again.
- Chowder is given food to make him more intelligent after Mung Daal gets tired of him being such a scatter brain. It works a little too well, with Chowder even realizing he's a cartoon character in a dumb cartoon, then uses his brain to change the show into a more educational, albeit boring, one.
- Pinky and the Brain: In "That Smarts", Brain made some calculations and concluded Pinky's lack of intelligence was the reason their plans to take over the world never worked. Brain then decided to make him smart with a machine so complicated to use it must be operated by already intelligent people. The newly intelligent Pinky soon pointed out erros in plans Brain showed him afterwards and concluded their previous failures weren't his fault. He then pointed out Brain's miscalculations from when it was concluded it was Pinky's fault. Brain was so annoyed he told Pinky to leave. Afterwards, Brain made new calculations and found out the previous failures were his fault. He then concluded one half of the duo had to be idiot and then used the machine to make himself dumb. Oblivous to this, Pinky decided to use the machine to revert back to his stupid self. Brain now had no idea of what they do every night.
- One episode of Dexter's Laboratory has Dexter deciding to increase Dee Dee's intelligence and make her his new lab assistant. To do this, he replaces her literally peanut-sized brain with a much bigger one. The operation is a success, but Dee Dee is now actually smarter than Dexter is. She tries pointing out flaws in his machines, but Dexter's ego prevents him from heeding her warnings. Finally, Dexter's behavior offends Dee Dee so much that she decides that working for him is beneath her, and so leaves him with a cymbol banging toy monkey, feeling that it would be a more fitting assistant.
- The Jimmy Two-Shoes episode "Beezy J. Genius" in which Beezy is struck by lightning from Heloise's Braniac Booster, He becomes an Insufferable Genius to everyone else by overthrowing his dad, abandoning Jimmy, and just annoying Heloise by doing scientifically impossible things.
Beezy: It's possible when you're this smart.
- In Episode 70 of Kaeloo, Stumpy is offered a wish by a spirit, and he wishes for intelligence. This results in "Flowers for Algernon" Syndrome, with Stumpy trying to Take Over the World. The spirit decides that Stumpy, who is a literal Cosmic Plaything, is more amusing as a moron and reverts him back to his normal, stupid self.
- On The Fairly OddParents, Timmy gets sick of AJ rubbing his grades in his face and wishes he knows everything. He turns the tables on AJ, even stealing his chair on the Academic Decathlon. However, that ends up being his undoing. As soon as the decathlon starts, Timmy loses his brains, since wishes can't be used to win contests.