"The children are suddenly surrounded by a couple of wildcats who prepare to slaughter the children until a man shows up on another bus with a rifle and shoots it at the wildcats. If none of this makes any sense, that's okay, since it's never referred to ever again."
Passepartout, in his joy on reaching at last the American continent, thought he would manifest it by executing a perilous vault in fine style; but, tumbling upon some worm-eaten planks, he fell through them. Put out of countenance by the manner in which he thus "set foot" upon the New World, he uttered a loud cry, which so frightened the innumerable cormorants and pelicans that are always perched upon these movable quays, that they flew noisily away.
There's that uncomfortable and unnerving "Vodka" chapter that comes the eff out of nowhere late in His Dark Materials. Will, a 12 or 13 year old boy, is traveling alone. He stops at the house of an old priest to ask for directions. The priest pushes him into accepting a drink of vodka, chats in an overly friendly manner, is very touchy-feely, tries to convince Will to stay a while and is just generally creepy. After few pages of this, Will insists on leaving and the man gives him a hug and lets him go. There is no mention of the incident or the old man ever again.
This was a jab at the Catholic Church, referencing their rampant sexual abuse of children.
In addition to a number of Wacky Wayside Tribe incidents, one can probably find a number of Big Lipped Alligator Moments in L. Frank Baum's Oz books. The first book, The Wonderful Wizard of Oz, has the China Country, where all the inhabitants are made out of china. Some of them, such as the singing china clown, have been broken and mended several times. They neither help nor hinder Dorothy and her friends, they are introduced out of nowhere and have nothing to do with the story, and they're never mentioned again in the book afterward (or in any of the later Oz books, for that matter). Things like this add to the unnerving dream-logic of the story. A surviving earlier draft doesn't include this adventure at all, and it may have been added just to pad out the book.
An example in Alice's Adventures in Wonderland is the scene where Alice sees a giant (compared to her) dog, fears it will kill her, but manages to distract it and escape. The dog is the only animal in Wonderland that doesn't talk or exhibit other human characteristics, the tone of the scene clashes with the surrounding scenes, and it is never mentioned again. This isn't ridiculous or over-the-top like a typical BLAM example, but it reads almost like a page from a different fantasy book. Not surprisingly, the Disney movie and most (all?) other adaptations leave it out completely.
There is a particularly narmful scene in Of Mice and Men where Lennie hallucinates that he is being berated by a talking rabbit. And his Aunt Clara.
The Lost Symbol has a chapter where the hero is unconscious... literally. Not mentioned again, not used, nothing, whole chapter = sleeping hero.
The episode of the dinner of Trimalchio in Petronius' Satyricon. It also happens to be the only passage that survives intact.
Earlier in the work, there's a scene where the main characters get drunk, are (forcibly) involved in an orgy, pass out, and wake up with their faces covered in soot. They vow never to speak of the incident again. Several other scenes might also qualify - the fragmentary nature of the work makes it hard to tell what is and isn't relevant to the plot. Or even what the plot is.
Mervyn Peake's Gormenghast series has many random scenes, where characters are introduced and conduct pointless dialogues, or new locations are visited and lovingly described, and are then never mentioned again.
Considering that he only finished two of the five planned books and only one additional one was made (by his wife), this might be a case of foreshadowing destroyed by Author Existence Failure.
A bizarre example from a nonfiction book can be seen in Black Like Me, the journal of a white man who changes his skin colour and observes the way he is treated as a Negro man, as he calls it. On a bus to Mississippi he encounters a black man named Christophe who sings Jazz, smiles at the white folk and snarls at the black folk, speaks perfect Latin, was training to become a priest, claims to be meeting his wife in another town and is planning on shooting several men and running away with his family. Straight out of nowhere, inexplicable, never mentioned again.
In the first or second chapter of Moby-Dick, Ishmael (the protagonist) is in a tavern, where there is a man named Bulkington, from Virginia. The way he's described makes him seem both magnetic and physically impulsive, and others in the bar are shouting his name. Then he's never mentioned again. (Even my English teacher thought that was strange.)
A commonly accepted theory is that Bulkington was intended to be a central character in a mutiny plot Melville originally planned but later dropped.
Also, Bulkington appears again in chapter 23, "The Lee Shore", steering the Pequod. And then there he's again never mentioned in the book once.
Oh course, this happens in Thomas Pynchon novels all the time, in fact, BLAM's may get more page space than the novel's "plot" itself, leading one to wonder whether it is, in fact, the plot of any Pynchon novel that is a BLAM to be compared against the self-consistent cohesion of the otherwise unrelated, ubiquitous absurdities.
As it goes on, Stephen King's The Dark Tower series starts to have more and more of these.
One that springs to mind is in the scene where Roland and Eddie meet Stephen King, who is a character in his own book. Now, that may sound Blammy but it all makes sense in the series' metafictional context. The BLAM here comes when Eddie comments that if King-the-character keeps smoking, he won't live long enough to complete their story. Roland then insists that smoking is good for you as long as you wait until you're an adult to start. Apparently it keeps away everything from insects to evil spirits that cause disease. It seems like it could maybe be a Chekhov's Gun, but it's never mentioned again. Fans of The Dark Tower were worried that King would die before he completed the series because he kept taking too long between books and he was a heavy smoker. Eddie is serving as a stand-in voice for the fans who want their story to be completed and Roland is a stand-in voice for King, who politely but firmly rebukes Eddie.
Mrs. Tassenbaum starts out as a Big-Lipped Alligator, coming out of nowhere with a long backstory. Then she finally meets Roland, and it becomes a Bizarro Episode when they eat fried chicken and have sex in a hotel room. She doesn't really help Roland, and perhaps her only purpose in the story was to get him to a hotel room where he could see a television and not be able to see anything but scan lines. There are more scenes like that, especially in the last three books.
In the children's classic The Wind in the Willows there's the infamous 'Piper at the Gates of Dawn' chapter, where the characters are transported into a mystical world where they meet the great god Pan. Many editions of the book omit this chapter, not because it's bad, just because it's so baffling in relation to the rest of the story. note It made a good debut album title, though!
'Wayfarers All', which involves Rat being hypnotised to run away to sea, but the Mole holds his friend down until he's recovered from the brainwashing.
Older Than Feudalism: At the end of book 19 of Homer's The Iliad, as Achilles hitches up his horses to go into battle, he prays that they will bring him back safely like they didn't do for his fallen friend. In response, the horse Roan Beauty suddenly gains the power of speech, simply to tell him "yeah, alright, this time. But next battle, you're doomed, buddy." Aside from a moment of surprise, Achilles barely seems to notice his brand-new talking horse; Roan Beauty loses speech as suddenly as he gained it, and the incident is never, ever mentioned again.
The Odyssey has a scene in Scheria where the poet Demodocus sings a comedic story about how Hephaestus trapped his wife Aphrodite and the latter's lover Ares in bed and then call the others gods to humiliate them. It has nothing to do with the story and never mentioned again. For many scholars this part may be a late interpolation.
In World Made by Hand there is a scene where Robert visits the New Faith congregation. While there, he meets an obese woman that has multiple seizures followed by prophecies. The general reaction readers appear to have to this scene is "what the hell?"
Deke McClelland's Macworld Photoshop 3 Bible (as the title implies, it's a how-to guide) pulls one off at the very end, after several hundred pages of Rapid-Fire Comedy: in the middle of a step-by-step guide to making a graphical effect, step 29 is a snippet of a suspense story about a spy sneaking through the dark. And halfway through, the Prime Minister pops up out of nowhere only to get shot. (So, a BLAM - both a figurative and a literal one, to boot - within a BLAM!) The author then goes back to Photoshop tips, commenting that he dislikes Step 29, since it's troublesome and makes all others look dull in comparison.
DOS For Dummies included, among its many how-tos on MS-DOS, step-by-step instructions on how to change a nappy.
The entire two or three chapters featuring the hobbits' adventures with Tom Bombadil in The Lord of the Rings is a very lengthy BLAM chiefly about singing excruciatingly bad folk songs and talking about how awesome Goldberry is. Actual connections to the plot of the rest of the book amount to: (a) the One Ring doesn't work on Bombadil - which gets one mention at the Council of Elrond — and (b) leaving the Old Forest you might trip over a wight and wind up with a cool Numenoréan sword.
May not qualify because the sequence with Bombadil and the wight does explain why the cool Numenoréan sword had enchantments on it capable of unbinding the Witch King's undead flesh and making him vulnerable to an ordinary sword long enough to be killed.
The Star Wars Expanded Universe book Darksaber features a particularly odd moment when Luke Skywalker and love interest Callista (an Old Republic Jedi preserved in stasis who has lost her connection to the Force) visit Hoth, where they are attacked by the wampa that had its arm cut off by Luke in The Empire Strikes Back. This wasn't explained at the time, but The Essential Guide to Alien Species eventually decided that wampas were semi-sapient.
In the middle of the original Gaston Leroux novel The Phantom of the Opera (well, at least in the original English translation,) a man on fire runs through an underground passage at one point, scaring the protagonists and then just as quickly runs right out of the scene and the novel and no one ever talks or thinks about it afterwards.
There are actually several bizarre encounters in the cellars of the opera house. They are all BLAM's to some extent, but their main purpose is probably to give the feeling that the protagonists are leaving the real world and are on the Phantom's turf now. Note that Christine's description of her first journey into the cellars, features some fairly strange and hellish imagery too. Some critics have seen the journey into the opera house cellars to be evoking The Divine Comedy, and Dante's descent through the Circles of Hell, so if this is the case, at least the BLAM's have some purpose to them.
Greg lampshades this in The Last Straw with Fregley coming out of nowhere with icing on his face and saying "BOOGIE! BOOGIE! BOOGIE!"
The Philosophy Club scene in the novel version of Gregory Maguire's Wicked. It seems like it should be a metaphor for something, but no one knows what.
A lot of Louis De Bernieres' Birds Without Wings could be said to be a patchwork of BLAMs. There is one scene where you see the sack of Smyrna from the point of view of one of the minor characters as he drowns, and the chapters about Mustafa Kemal Ataturk contribute to a feeling that the whole book is merely filler with a few relevant chapters pasted in. Even the character through whose eyes we see much of the Ottoman experience in World War One is not the character who then goes on to go mad and kill his girlfriend.
After an assassination in the Vietnam War novel War Dogs, the group's leader is returning from his watching post and is suddenly attacked by a tiger. After an extended river tiger fight, he regroups with his team and almost no time is spent discussing his fresh wounds.
The two-dimensional planet stop in A Wrinkle in Time. The heroes "tesser" to a weird place where the children feel squashed and can't see anything, one of the adults mentions something about the kids being unable to exist properly on a two-dimensional planet, and they warp away. It was probably supposed to be related to the four-dimensionalness of their teleporting method, but no actual explanation is given for why they went there, what the heck a "two-dimensional planet" even is in a three-dimensional universe and why the kids weren't crushed to death.
On the other hand, they all lead to the scenes were Voldemort's point of view and thoughts seep into his mind. Perhaps it only works during REM sleep, or when his mind is particularly unfocused?
Dreams are often just like that - you do weird things with people who suddenly transform into someone else, then you wake up and go huh? Though why it was necessary to tell us his weird dream and then go into the dream about Voldemort I have no idea.
Harry's dreams are actually quite cleverly written if you look closely, as all the weird things in them are warped reflections of things that have recently happened to him. Take the above example: Harry recently went on a disastrous date with Cho where she unfavourably compared him as a boyfriend to Cedric several times, after which Hermione criticised Harry's own conduct; Harry's Firebolt is in Umbridge's office, as it's been confiscated; and before the last DA meeting Harry had to hurriedly dismantle a Christmas display Dobby had put up consisting of baubles emblazoned with pictures of Harry and the legend "HAVE A VERY HARRY CHRISTMAS!"
And it shows why Harry (and therefore the reader) takes his dream about Arthur Weasley so seriously: it's different. He starts out with a normal dream, made up of bits and pieces of the last couple of days (though not his date with Cho, that happens later) where everything doesn't quite make sense, and then suddenly he's a snake in a corridor attacking Arthur Weasley. If we just read about this on its own, it would be much easier to dismiss it as "just a dream" - a giant snake attacking Mr Weasley does sound like "just a dream" - but because we have the contrast it gets a coherence it wouldn't otherwise have, and we believe Harry when he says that someone needs to find Arthur urgently.
In The Help there is a scene in which a naked man attacks Minny and Celia at Celia's home in the country and tries to rape them. He immobilizes Minny, leaving Celia to fight him off by herself. Then he wanders away, never to be seen again. Presumably this scene was included to show that Celia is tougher than she looks and can fight for herself, but it's pretty jarring and really has no relevance to the rest of the story.
An example of this is to be found in the illustrations of C.S. Lewis's The Lion, the Witch, and the Wardrobe. The illustrations were done by Pauline Baynes, who in every single drawing of Aslan, depicts him as a lion walking on all fours. However, in the aforementioned book, there is one picture of Aslan and the White Witch discussing the terms of his surrender - which has Aslan standing on his hind-legs, his front paws clasped behind his back in a strikingly human-like pose. He is never described as doing this in the text, it's completely at odds with Lewis's emphasis on his leonine nature, and it's the only illustration in the entire seven-book series which portrays him taking such a stance.
Perhaps this human-like pose is an early hint as to Aslan's secret identity?
In Dealing With Dragons, when Cimorene is running away from her unwanted marriage, she follows a talking frog's advice on the way to go. Along the way, she passes a fancy pavilion where an unseen person invites her to come in and rest. Though Cimorene is tired and tempted, she remembers that she was specifically warned to stay away from the pavilion. She walks past it and...that's it. Nothing else comes of her not falling for it, there's no indicator of what would have happened, and the pavilion and woman in it are never brought up again. The only purpose of the incident is to give another example of how Cimorene is practical and Genre Savvy.
The Bible's Book of Exodus has the much-debated "Zipporah at the inn" episode which is no longer than three verses. En route to Egypte, Moses and his familly stay at an inn. The Lord tries(?) to kill him for unexplained reasons (right after He gave him the mission to free Israel). Moses' wife Zipporah takes a sharp stone, and cut off the foreskin of their son. The standard interpretation of the passage is that God wants to kill Moses for neglecting the rite of circumcision of his son but it's not stated explicitely and the incident is never mentionned again.
In the Gospel of Mark, there's a guy running naked during the arrest of Jesus. Some scholars have claimed that this man was Mark himself, the author of the gospel.
The House of Night: Um, why is Erik the new Tracker? How is he the new Tracker? A Tracker hasn't appeared since page 2, Book 1...
In Chosen, Zoey has two guys run down with a truck just because they posed a threat to Heath. It is never mentioned again.
Near the end of the first part of Don Quixote, the characters are at and end and spend two and a half chapters reading a story story they found in a chest which has no bearing on the main story. Early in the second part its outright said that it was a pointless digression that broke up the flow of the narrative for no purpose.
In the Nancy Drew novel Mystery of the Brass Bound Trunk, Nancy is struck by lightning after getting caught in a freak-storm while on a picnic with her friends. It has no bearing on the rest of the story, it's over in less than a paragraph, and no one ever mentions it again afterwards.