The guys who wrote The Anarchist Cookbook left out crucial components that would have made things work properly (and dangerously), except their aim was allegedly to get people hurt.
Arly Hanks: After describing the aftermath of a kitchen grease fire in Maggody and the Moonbeams, Arly warns readers not to set off fire extinguishers indoors to find out if her description is accurate, or they'll be sorry.
Curious George: "George is a monkey, and he does things we can't do." One of the books goes through the consequences of what happens when George eats a puzzle piece, thinking it might be candy- hospital visit included.
Dave Barry's Guide to Guys parodies this in a footnote to a passage overendowed with metaphors: "I am a professional writer. Do not try these metaphors at home."
The Taming of the Screw (a spoof home-improvement guide) has a number of instances where he tells you not to try something yourself. "Have your neighbor do it."
Aside from the Good Omens quote at the top of the page, Terry Pratchett pulls this trope in Interesting Times: When fireworks are mentioned, Rincewind tries to clarify as "The sort of thing where you light the blue touch paper and stick it up your nose?" The helpful footnote on the same page reads, "KIDS! Only very silly wizards with very bad sinus trouble do this. Sensible people go off to a roped-off enclosure where they can watch a heavily protected man, in the middle distance, light (with the aid of a very long pole) something that goes 'fsst.' And then they can shout 'Hooray.'"
A message from the author. Not all cauldrons are metal. You can boil water in a leather cauldron if you know what you are doing. You can even make tea in a paper bag if you are careful and know how to do it. But please don't, or if you do, don't tell anyone I told you.
An in-universe example of someone not getting this warning: in Reaper Man, we learn that Sergeant Colon's favourite story as a child was The Water Babies and he had always wondered whether it was really that interesting underwater. (Windle Poons, having unsuccessfully tried to drown himself, assures him that it isn't.) In a later book, Colon reminisces that the first time he went to the seaside as a child, he tried to breathe underwater because the little boy in the story could, and he didn't know that it didn't work in real life.
James Randi's An Encyclopedia of Claims, Frauds, and Hoaxes of the Occult and Supernatural contains an entry on fire-eating which states "Do not try this at home."
Roald Dahl's George's Marvellous Medicine begins with a warning to children not to follow the protagonist's lead and start mixing up things they find in their medicine cabinets at home and drinking them because it might make them sick. Or well and truly dead.
The commentary to several of Mercedes Lackey's Heralds of Valdemar books discusses the author's love of equestrianism and falconry, and in one notable case is careful to point out that the Tayledras bondbirds and Valdemaran Companions are not normal animals and people should not go into these pursuits expecting real animals to behave like that.
A variation found in How to Mix Drinks by bartender Jerry Thomas. One drink, called the Blue Blazer, requires the drink to be set on fire before being poured back and forth between two mugs. The end of the recipe contained a warning that novices at this drink should practice the pouring with cold water before attempting this; that way, the inevitable slip-ups would only get the novice wet.
After a comment that the father's role in the family is as protector, so all men should sleep with a 9mm under their pillow and "wake up firing" at any sign of movement:
Footnote Fever struck again when Stephen huffed Axe body spray on screen.
Bullet Point: Do not try. Professional breather in closed bag.
Every instance of someone climbing into the eponymous wardrobe in The Lion, the Witch, and the Wardrobe, is accompanied by the narrator's remarks on how dangerous it is to close oneself into a wardrobe, how smart Lucy and Peter are to leave the door ajar, and how foolish Edmund is to close it on himself — no doubt to prevent children from getting themselves trapped in wardrobes while trying to emulate the Pevensies. This becomes Hilarious in Hindsight as of the Walden Media movie adaptation: one of the outtakes has Skandar Keyes (Edmund) climbing into the wardrobe and closing the door behind him... and getting locked in.
Spoofed to high heaven in the first Franny K. Stein book Lunch Walks Among Us at a section where the reader can cut three pages to mix and match different recipes for creating a monster.
WARNING— We assume no responsibility if you actually create a real monster and it destroys your city and eats your stuff.
The Mermaid Variations: When Caroline greets a walrus, the author notes, "When meeting a walrus for the first time you should always shake it politely by the tusk, but only in a story, never in real life."
Nation features an afterword discussing the truth behind some implausible-sounding things that happen in the story; most of them are accompanied with warnings that you should not try this at home. The last one, instead, says "Thinking This book contains some. Whether you try it at home is up to you."
Matthew White & Jaffer Ali's The Official Prisoner Companion's comment on a plot point in The Prisoner (1967) episode "The Girl Who Was Death":
In an early scene Number Six thinks he's been poisoned. One of the big trivia questions surrounding the series concerns the names of the different drinks that Number Six consumes as an antidote to the poison. What were the drinks? In the appropriate order, they were brandy, whiskey, vodka, Drambuie, Tia Maria, Cointreau, and Grand Marnier. Don't try this at home, folks.
Pretty much everything Ragnar Benson has ever written is encrusted in warnings that the book in question is for information purposes only and that attempting to actually apply the instructions found within could easily result in a long stay in prison, hospital, or prison hospital. It's probably worth noting at this point that Benson's works include Homemade C4: A Recipe For Survival, The Most Dangerous Game: Advanced Mantrapping Techniques, Ragnar's Guide to Home and Recreational Use of High Explosives, Breath of the Dragon: Homebuilt Flamethrowers, Home-Built Claymore Mines: A Blueprint For Survival, David's Tool Kit: A Citizen's Guide to Taking Out Big Brother's Heavy Weapons, and Homemade Grenade Launchers: Constructing the Ultimate Hobby Weapon.
The Red Green Book describes a fictional "game" that essentially involves drinking oneself into low-level alcohol poisoning. Understandably, that section of the book contains an editor's note that says "Do not, under any circumstances, ever play this game."
A Series of Unfortunate Events: the second book, The Reptile Room, warns the reader to never, ever, ever, ever, ever (continued for slightly more than a page) ever stick things in an electric socket. Ever. We are warned precisely 209 times. In the third book, The Wide Window he explicitly warns the readers that if they ever need to get to Curdled Cave in a hurry, not to steal a boat and attempt to sail across a lake in a hurricane, which is precisely what the protagonists are doing.
In Sewer, Gas & Electric, when Morris Kazenstein appears in Dufresne's eco-activist video, he warns kids not to try what he's about to do without parental supervision. Namely, sink an illegal whaling ship with a magnetic railgun that fires whole kosher salami.
In The Shadow pulp series, The Shadow infrequently uses a substance he calls "The Devil's Whisper" — an explosive mixture smeared on his thumb and forefinger that explodes violently when he snaps his fingers. In one story, Maxwell Grant leaves this note: "Note: The explosion from the fingertips, produced by the action of two chemicals, is terrific in its power. It is extremely dangerous in use; for an over-amount, even though seemingly slight, will produce an explosion with the effect of TNT. The Shadow has used it but seldom; on those occasions, with the strictest care. Properly produced, the explosion is so instantaneous that the operator remains uninjured. Because of the danger from these chemicals, I have never made a copy of the formula; and can answer no requests concerning it. ~Maxwell Grant." "Grant" is actually Walter B Gibson, who was, among other things, a professional stage magician. "Devil's Whisper" is a rarely-performed real-world magic trick that is extremely dangerous — if done wrong, the magician would lose fingers at a minimum. The note may have been an attempt to keep curious readers from researching the trick.
In China, there exists the proverb "The young should not read Water Margin, and the old should not read Three Kingdoms". This proverb came into existence because the former depicts the lives of outlaws and their defiance of the social system and may have a negative influence on adolescent boys, as well as the novel's depiction of gruesome violence. The latter presents every manner of stratagem and fraud and may tempt older readers to engage in such thinking.
