The hit XBLA and PSN game Castle Crashers pretty much built its empire on BLAMs. One particularly memorable one happens near the endgame: one of the three bosses you have to fight before taking down the Big Bad is a wacky, robot-voiced painter with a toolbox for a head. He descends from the scaffolding in his room to paint on a big canvas on the wall which makes his art come to life and attack you. Among things he draws are a snail with a nose for a face, angry elephants, eyeless unicorns and Carrot Clock.
If you're familiar with Newgrounds, Castle Crashers' pedigree, you might recognize many of this "art" from particularly bad flash portal entries.
At another point in the game, your characters are abducted by aliens (in a medieval setting) with absolutely no warning whatsoever. After you escape and destroy the squadron of aliens that follows, a large alien sitting on a toilet pumping a dumbbell suddenly runs over to the console and destroys it for no fathomable reason, forcing a self destruct sequence. This incident is never mentioned again, save for a cameo in the ending. The alien is the main character from The Behemoth's previous game, Alien Hominid. And much like there, they're all One Hit Point Wonders. Sort of a Big Lipped Alligator Moment cameo for the alien.
In Devil May Cry 4, After Dante beats Berial, you're treated to a wonderfully dirtycutscene where Dante demonstrates his new weapon.
There's also the Dante vs. Agnus battle. The cutscenes before and after are, for no reason other than Rule of Cool, a perfectly sung improv opera scene. It's awesome, but completely out of nowhere. Take a gawk.
And the Jester boss fights in Devil May Cry 3: Special Edition. Less challenging, more surreal, and less rewarding than the normal boss fights, and your opponent explicitly doesn't want you dead.
The MMORPG Everquest 2 has a Call Back in the form of the Tower of the Drafling, which seems to be a BLAM to many players. In the middle of a rather overrun contested area, is a beehive. Clicking said beehive shrinks you down, and allows you to explore and fight inside it.
The NPC that mumbles with the name '?' is likewise never explained.
In Metal Gear Solid 4, Big Mama goes off on a tangent comparing The Boss to the Virgin Mary, and Big Boss to Jesus, quickly adding pseudo-religious imagery to the mix of MGS4's "WTF?" moments. This angle is never ever mentioned again.
In Metal Gear Solid 3, after you defeat The Fury, he shoots himself up into the ceiling, killing himself. That's not the weird part. After that, his body falls to the ground and explodes. That's not the weird part. The weird part is when the flames of his body inexplicably shoot out two screaming heads made of fire, which chase Snake around yelling "Fury!" before crashing into the scenery and causing it to collapse, cutting Naked Snake off from the room where the battle took place. Even for the Cobras it was weird (especially because unlike the rest of his unit, The Fury was a badass normal with absolutely no supernatural powers, making it even more nonsensical).
Subverted in Metal Gear Solid 2. After getting captured and sent to Arsenal Gear, Raiden keeps getting a series of ever-increasingly bizarre Codec messages from Colonel Campbell and Rosemary, including the string of gibberish ending with a demand for scissors, 61! Turns out that Colonel Campbell and possibly Rose are both in fact the AI GW, which is suffering from the effects of a destructive computer worm. The ending, however...
The Taito arcade game Pu Li Ru La has the player characters given the ability to cause a Big Lipped Alligator Moment as a Smart Bomb style special attack to clear the room of enemies. Seriously.
These include sudden animal rampage (complete with tribal chanting), a purple guy made out of jello appearing and attacking everything by doing ballet twirls at them, and a Mexican wrestler appearing in a giant microwave, catching everything (except end bosses) in a giant ball of yarn, throwing them into the microwave, closing the door, waiting a few seconds for the microwave to ding and releasing them back as animals (which is what the enemies normally turn into when defeated, and which can be collected for extra points before they run offscreen).
The Kill Sat sequence from Resident Evil: Dead Aim. See here. Essentially, a Chinese agent is sent to stop a terrorist. During her mission, China later decides to negotiate with him. For some reason, this means she is now a target of the Chinese government, specifically their laser satellite. (Why they would kill a loyal agent because they canceled her mission is beyond me.) She avoids the laser and the game's protagonist removes the GPS tracking device from her body. After that the whole "enemy of my own government"/killer satellite thing is never brought up again in the game.
Of course, this being Sam & Max, it was completely intended as one big BLAM for the player, much like the Conroy Bumpus song from Sam & Max Hit the Road.
The Mariachis in Season Two seem like a series of BLAMs at the beginning. Everything is explained in Chariots of the Dogs, where they're actually the episodes big bads.
This. How or why he was in space is never explained.
In Iji, there is the trippy Sector Z, a sector made up of a few of Daniel Remar's other games. You get there by finding all ten hidden posters, then by making a Tasen blow a hole in a cracked wall. When you find the teleporter pad, you'll also find a logbook that briefly describes how the sector was found. If you play through Sector Z in a normal game file (not single sector play), you turn up in the beginning of Sector 2 when you exit. Dan asks Iji where she went, and she says that she doesn't really know, and only remembers some kind of rave or mosh inside a video game console. When Dan remains silent, Iji tries save face by giving a more technical explanation, but is interrupted by Dan saying, "You know what? I'm going to pretend this conversation never happened." It is never brought up again during the rest of the game, as if it never occurred.
This would probably count as an Easter Egg.
At one point in Kagetsu Tohya Shiki randomly gets eaten by a magical talking jaguar for going through Arcuied's underwear. What the hell is going on here? Even Shiki is baffled. And unlike numerous other bizarre things in this Oddly Named Sequel - though it's far from the only example - this never comes up again or is explained in the slightest.
It is a dream after all.
In Super Mario RPG you can go behind a curtain in Booster Tower which turns Mario into his 8-bit version. The theme from Super Mario Bros. starts to play and you are able to wander around the room until you turn back to your normal self after running back behind the curtain after trying to enter one of the doorways.
This BLAM is repeated once per game in the first two Paper Mario games. Super Paper Mario upgrades it into two new powerups — one causes the characters to become giant hulking (and pixelated) 8-bit versions of themselves, while the other causes small 8-bit allies to follow the character. However, the developers wisely threw in a BLAM regardless; in one scene, a koopa grabs the giant powerup and chases the player across the stage until he or she finds a giant powerup as well, and can then fight the koopa on equal footing.
The "That's My Merlee!" sequence from Super Paper Mario also qualifies. Basically, you're trying to find this woman named Merlee, but the chapter's villain is a shapeshifter who assumes her form. When you finally meet them, the game bursts into a game-show spoof sequence where you try and deduce which one is the real Merlee. It's completely out of nowhere, is never mentioned again, and to top it off, the biggest giveaway as to the real Merlee (a fly buzzing around her) has nothing to do with the sequence at all. And the abovementioned sequence, as well as the corresponding boss battle, all take place in a women's public restroom. Seriously.
Super Mario RPG has a second BLAM in Merrymore. You save Princess Peach from Booster, but then a pair of chefs fight you because you destroyed the wedding, nullifying all the work they put into this freaky cake they baked. They attack for a few turns, and then the cake comes to life and attacks the party while the chefs run off. After beating it, Booster comes in and eats the cake whole and the party moves on without ever mentioning the incident ever again. It doesn't help that the cake is also a That One Boss for many.
Later in Super Mario RPG, there's the Mirror-Mario encountered on the Sunken Ship. It doesn't attack you unless you "talk" to it, which makes it reveal its true form, a Boo. All it does is provide a rather easy obstacle to get past and a stepping stone to get to a hidden treasure box, and not once is it ever explained.
In Parappa the Rapper 2, Chop Chop Master Onion from the first game has a show that's "Strictly for Adults" in which CCMO teaches "romantic karate". and Parappa and his best friend PJ try using the moves on each other while unbeknownst to the two of them, Parappa's father and girlfriend's father watch. This is never mentioned again. Lyrics include "Caress your lover," "Let's get it on," and (while Parappa is holding PJ) "Lovers, we are." This is one eighth of an E-rated game.
Gore Ultimate Soldier is a fairly standard space FPS. SUDDENLY, HORDE OF YELLING SKELETONS WITH CHAINSAWS, WHAT DO YOU DO?
Supposedly, the game is about some virtual reality training simulator that goes wrong. Not that it matters that much if you're playing a game called Gore: Ultimate Soldier.
Mega Man Star Force 3 had the most random appearance of Hyde/Dark Phantom... ever. He kind of shows up, says Geo ruined his life, is defeated again and falls off the Wave Road (wait, you could fall?). And then... never ever mentioned again.
Not COMPLETELY random. It happens during the same sequence of events where you are busy trying to put Luna back together again. Considering how much he seems to be connected to Luna, there might be something more to it...but either it was lost in translation or not established due to bringing back Luna being a more important plot point. But it's still a BLAM considering he seems completely unaffiliated with anyone this time around, and is never brought up again since everyone is glad to have Luna back.
The Mega Man Battle Network games are FULL of BLAMs, but one in particular truly stands out: in MMBN2, a deadly spider gets loose on an airplane, and Lan has to help trap it. The spider incident has absolutely no bearing on the game's plot, is an utter waste of time, and even worse, features a BLAM within a BLAM in the form of the whiskey event◊.
Honestly, you could make a strong case claiming that the entirety of Battle Network 4 was a BLAM. See the main article for an explanation.
Pokémon HeartGold and SoulSilver feature an optional event where an entire UNIVERSE is created and presumably destroyed in order to give you a rare Pokémon. Proof here. And from the first Updated Re-release of Gold and Silver, Pokémon Crystal, we have the above-pictured opening of the latter. Pure Mind Screw: it doesn't even get a proper Mind Screwdriver as a plot point within the game itself, where the Unown and Suicune are completely unrelated.
In Sonic Adventure 2 while playing the Hero Side (or Light Side) Story, after you have completed the 'Death Chamber' Stage where you play as Knuckles, You -as Knuckles- have a sudden encounter with a giant ghost named in-game as: King Boom-Boo,King of ghosts with whom you then have a Boss Battle with which involves getting behind Boom-Boo to attack an - in-game described - 'Baby Ghost' who is holding an hourglass switch which opens overhead trapdoors that let sunlight in, which when opened, will weaken King Boom Boo into a smaller state which can allow Knuckles to attack Boom Boo. King Boom Boo does not bare any other coherent relevance to the rest of the in-game plot or scenario and as soon as Knuckles is done fighting Boom Boo and he disappears, Knuckles just shrugs it off and King Boom Boo is never mentioned or referenced anywhere else in the whole game (and probably never any other Sonic game) after that.
Final Fantasy IV has the dancing girl, who randomly turns into a monk and then proceeds to run around in the inn, like (s)he was trying to get a touchdown, complete with fitting music. She returns to normal afterwards. You can watch the scene multiple times, but the only comment ever made on it by anyone is Cecil's dumbstruck "What the—?!"
And there's the entire cafe in Troia, which features no plot relevance and only exists for a few funny lines, plus an expensive "pass" that will get you into the strip club in the back.
Dirge of Cerberus: Final Fantasy VII is packed full of narmtastic moments, but it truly crosses over into BLAM territory when Lucrecia brings up (out of nowhere and apropos of nothing in the plot) how she was responsible for accidentally killing Vincent's father and proceeds to show Vincent a vision of how she did it. Vincent is not really bothered by hearing this and it's never spoken of again.
During the trip to the Fourth Ranked Battle in No More Heroes, Travis falls asleep on a train. This causes him to... dream of playing a Bullet Hell shooter based on his favoriteCute Witch/Giant Mecha show. And no, the following battle has nothing to do with said anime, or shooters. It just is.
No More Heroes 2: Desperate Struggle has one after the seventh ranked battle. You play as Henry, as he dreams about a very Moe girl with a jetpack thing with arms trying to kill him. Never comes up again.
The warp points from Star Fox 64, which are eerie, tie-dye stages-within-a-stage with bizarre music in the background. Your normally very chatty team is completely silent throughout and after each warp point, with literally the only indication that they exist and what you just played wasn't some bizarre, spin-induced hallucination being a few lines in Sector X concerning opening a 'gate'. The first thing out of anyone's mouth before entering one is guaranteed to be some variant of "What the...?"
Don't forget the "Out of This Dimension" stage from the original Star Fox on the SNES, which took Fox and company to some bizarre plane of existence with colored floating heads in the background, paper airplanes attacking you, and a giant slot machine for a boss. You defeated it by shooting the handlebar to make the reels spin, shooting the buttons to lock pictures in place, and eventually lining up triple sevens, at which point it would shoot meaningless coins at you and then explode. The end credits would then play without any real closure to the plot, leaving players wondering just what they had played through, and what happened to Andross or Corneria. Also unnerving is the intro text to the stage, which reads "Come in, Arwings!! Fox, where are you?!! We need you to protect Corneria!!"
BLAM-mania finds itself at home in the Guilty Gear series, though considering the bizarre cast of characters, not much sense COULD be garnered from anything even if we tried. Either way, this one counts the most due to its confusability and its status as never being mentioned again: One of Sol Badguy's story routes in Accent Core Plus has him being forced to fight his past self (Order-Sol) by I-no. After the fight, I-no kills Order-Sol, but in one route, Sol remains in existence somehow. The whole thing is never mentioned against Sol ends up in another fight with Ky Kiske (they fight a lot in the series). This is in contrast to the other ending, where his past self's death naturally negates his existence.
It's impressive for a game that's already as out there as Banjo-Kazooie to have a Big-Lipped Alligator Moment, but there you go: for the final phase of the final battle, after Banjo and Kazooie have exhausted all their options — even the Jinjos have taken their shot — and Gruntilda is still standing...out of the center of the arena sprouts a gigantic Jinjo statue, which intones in the Voice of the Legion"I AM THE MIGHTY JINJONATOR, ACTIVATE ME..." Doing so has the Jinjos combine their power into what is, assumedly, the Jinjo version of the Terminator, which proceeds to wallop Gruntilda but good, sending her falling to her doom. This is never foreshadowed, explained, or brought up again throughout nearly the entire series, except for one Jinjo in Nuts & Bolts talking about how he wants to train to be as powerful as the Jinjonator. One measly Jinjo — that's it. Twelve years later and lots of development for the Jinjos, and we still don't know what the heck was up with that and probably never will.
Sierra is already fond of lateral thinking puzzles, puns, and visual gags, so off-the-wall moments don't usually qualify, except this one. In the later half of King's Quest VI, Alexander, becoming more and more desperate to Save the Princess, journeys to the underworld, an understandably solemn place. To get the guard to give you his skeleton key, you must play an upbeat tune on a conveniently-placed bone xylophone, causing all four guards to jiggle and dance, also causing three more skeletons to can-can onto and off of the screen. Then it's right back to the dreary music, you pick up the key, and go on your way.
Quest for Glory III has a couple, including a nighttime encounter with Arnie Saknoosen the Earth Pig (possibly a reference to Cerebus the Aardvark) and being attacked by the Awful Waffle Walker if you wander around the savannah without food long enough.
In Jak 3, there's a scene where Daxter gets sucked into a computer and has to play a Pac-Man style game to find a MacGuffin. It evidently wasn't supposed to be that much of a stretch, since the character who put him into the computer was one with the computer himself, but Daxter's whole body getting sucked through the screen?
In Gearsof War 2, The Squad go to an Abandoned Government Facility to get the Locust Stronghold, where they find genetically engineered hybrid-monsters, and that the lead scientists have went to the path that the Squad must go through. The Creatures, people, and threat are never mentioned again.
This was supposed to be explained in 3, but was cut for some reason. Word of God is that Myrrah, the human queen of the Locust, was the daughter of one of the scientists at that facility and was experimented upon. She fled to the Hollow and rallied the Locust behind her. So yes, the primary motive of one of the series' main villains had to be explained in a forum post.
Devil Survivor has an event called the "Miyashita Koan", where a weird clown-like demon named Ghost Q challenges you to look for treasure hidden in one of the three memory cards he has scattered throughout the stage. Once you complete the battle (either by finding the treasure, Ghost Q giving up on you and leaving, or outright killing Ghost Q), this battle is never mentioned again.
Mother 3: "Lucas opened the present. You heard a mambo rhythm. Ah."
"Lucas opened the present. An indescribable smell lingers in the air. Ah."
The Legendof Zelda Majoras Mask has another BLAM blocking your access to the Snowhead Temple. A seemingly-sourceless icy wind repeatedly blows along the long, winding narrow path that leads to the temple. You put on the Lens of Truth, and see... a giant invisible Goron, sitting on the side of the temple and blowing cold air down the path. Why is there a giant Goron sitting on the temple? Why and how is he invisible? Why is he blowing on the path, and why is his breath an icy blizzard? How do Gorons even get that big? None of it is ever explained. At least he survives the fall.
The Legendof Zelda Links Awakening has a rather unusual moment when you go inside Ulrira's house and try to call out from his phone, rather than trying to call him from one of the many phone booths. Who or what is a Bucket Mouse? Why would Ulrira apparently have him/her on speed dial? He/She is never shown or referenced anywhere else in the game, so it's anyone's guess.
BRRING! BRRING! BRRING! CLICK! Yeees! It's the Bucket Mouse! Thanks for calling! ...Well... CLICK! ??? ... You must have dialed a wrong number...
The Giger-esque alien's lair at the end of the arcade version of Astyanax.
In Trauma Center: Under the Knife, the gameplay generally involves performing operations. But in one level, you have to defuse a bomb, using the exact same equipment and methodology as the operations. This is from an organization that primarily works via an evil living virus; a bomb doesn't seem like them.
Phantasmagoria 2 has gangsters dancing past a bondage club before you enter. In a (supposedly) serious horror game. There's also Batman visiting the psychiatrist, but that's an Easter Egg anyways (the fact that it's so poorly integrated could easily make it a BLAM, though).
Halo: Reach: In the mission, Nightfall, we get two, fifty-foot tall, great, gorilla-looking beasts. They attack the Covenant, and when they're through, for absolutely no reason, they go after you. The so-called "indigenous species" are never ever referenced before or after.
The creatures were supposed to show up in more than just one level, but were ultimately cut from the game except for this one part.
Apparently, Wicked K was added at the last minute as a developer in-joke.
The SNES version of Aladdin has two strong contenders for this. The first stage, in which Aladdin is sucked into the Genie's lamp, seems the more obvious example due its bright and trippy nature in contrast to the rest of the game, but it's somewhat justified in that a) this covers the "Friend Like Me" sequence from the movie, and b) you have to do it before Genie will let you out of the cave. The other example is the Egypt stage, where Abu accidentally falls off the magic carpet during their trip back to Agrabah, and Aladdin must find him inside an Egyptian pyramid. It's definitely not as outlandish as the former example, but it more obviously has no bearing to the rest of the plot and is clearly there to just pad the game's length.
The Genesis version has a similliar stage involving a lot of platforming with springs and bumpers, with a mountain of random items in the background. The exit is Genie's open mouth, with his tongue forming the stairs.
One bonus area in VVVVVV includes a flickering elephant so big its body spans four screens. It causes the player character to adopt a sad expression while standing near it, but otherwise has no significance whatsoever.
It could be argued that the events generated by the "Wacky Wasteland" perk in Fallout: New Vegas are these. An arguement that is very well founded, may I add.
It's probably best to treat the entirety of the "Mothership Zeta" content in Fallout 3 as one as well.
The game for Scott Pilgrim vs. The World has one in Roxie's stage where in a Japanese steakhouse random people on fire come out of nowhere and run around until you kill them, or they accidentally run onto the damaging grills. This never really happens any other time in the game.
World of Warcraft: Cataclysm has several quests that pop out of nowhere simply because your character decides s/he doesn't like a particular critter inhabiting the area (hyenas, buzzards, eels, etc...). Once completed, you congratulate yourself on a job well done. And it is never mentioned again.
The instruction manual to Totally Rad features a few. In the midst of a lengthy explanation of the game's Excuse Plot, the manual inserts random pictures of an old airplane and the boss of Jaleco Entertainment's USA branch. Another one next to the controls is a picture of some lady — no explanation as to who she is except the writer forgot he put her in there. It's easy to tell that Jaleco USA was having way too much fun with the game itself.
Bookworm Adventures Volume 2 has the "Dance Battle" level near the end of the game. Lex battles while dancing to the funky music. With robots. It somewhat justifies its existence by not being too easy to beat, since it's a Survival Battlenote meaning you aren't allowed to recharge the health meter between the enemies, but that doesn't change the fact that it comes completely out of nowhere and is absolutely hilarious. It does, of course, advance the game progress by giving you a companion, but there was no reason for the level to take that form. "Beyond their wildest imaginings", as the level intro puts it, is very much an understatement.
Stubbs the Zombie has a level where you and your horde of zombie minions fight your way through a police station, culminating with you taking on Police Chief Masters ("Chief Masters", by the way, is one of several nods in the game to the fact that it runs on the Halo: Combat Evolved engine). When you finally corner Masters, he... challenges you to a dance-off that plays out like the classic memory toy 'Simon'. None of the other boss fights are particularly unusual, you just fight them with the usual controls, like every other enemy. It's just Masters who makes it into a minigame, and it's never mentioned again (although to be fair, the main character is an unspeaking zombie, so the game doesn't really have much by way of plot).
The Great Mighty Poo [in a nice operatic baritone]:I am the Great Mighty Poo, And I'm going to throw my shit at you. A huge supply of tish comes from my chocolate starfish. How about some scat, you little twat?
Vanquish is generally a fairly serious game, but at one point, you sneak behind some crates and observe a dance off by a whole platoon of robot soldiers, accompanied by a giant white boombox. As soon as one sees you, they act normally and the boombox converts into a walking barrier with guns. It never happens again, nor is it ever mentioned.
While most of the bosses in the Xbox Ninja Gaiden games can come out of nowhere and have no bearing on the plot, the most notable are the Buddha and Statue of Liberty bosses added in Sigma 2. The Buddha is especially jarring since Ryu saves Sonia from her fall like in the original, then the statue returns, Ryu puts it down again, then Ryu goes and unties Sonia with no mention of the GIANT BUDDHA STATUE that Ryu just broke with his sword.
The game Blood Wings: Pumpkinhead's Revenge is all around weird, but if you let Marcie (Soleil Moon Frye) die, she'll appear in a cinematic as a cloaked figure just like everyone else you let die, but then she says "I am the key to your future" and then laughs maniacally for no reason.
Embric of Wulfhammer's Castle has the Ancient Scotch sidequest. It starts with randomly drinking a bottle of scotch in the "trophy room", devolves into a Cosmic Horror Story with overtones of Demonic Possession, then ends abruptly without actually resolving or explaining anything. While nearly everything else you can do in the game comes up again at some point in the story, this whole episode is only spoken of again in the Developer's Room. Nevertheless, it's brought up in the demo version of the sequel. As the explaination of why one of the maids never aged.
Dragon's Lair II: Time Warp features a series of odd levels as you guide Dirk the Daring through time to rescue Princess Daphne. But none however, are quite as strange, (and that's saying something), than the 5th level when Dirk is not only sent back to the year 1804, but is for some strange reason, shrunk down to the size of a mouse in Ludwig Van Beethoven's study, as the famous composer plays on a piano. During the level Dirk must avoid the composer's hungry cat and from there, it gets weird. Yes, weirder than that. Suddenly Beethoven, his piano, the cat and Dirk are sent flying into the air. The level gets even more chaotic as the cat suddenly starts breathing fire. And as one final cherry on top of this sundae of weirdness, Beethoven suddenly opens his coat and his outlandish clothes underneath make him look like Elton John. As soon as all this ends, Dirk suddenly finds his time machine, he's transported away and the level ends. None of this insanity is ever mentioned again.
In Chibi-Robo, using radar in the living room will eventually lead you to a dig spot in the carpet. Digging into it will reveal a tiny fat blue man with a spark plug for a head in a purple speedo, who will rave at you to "give him sound", which you do by jabbing him with your shovel-spoon repeatedly, causing him to dance as he rapidly grows to several times his size before thanking you and disappearing. You can repeat this any time you enter the living room, it is the only situation in which he appears and doesn't receive any reference or allusion anywhere else, and only Chibi and Telly seem to have any idea he exists.
"What If?" mode in the 2000 Spider-Man video game for Nintendo 64 and PlayStation. Words cannot describe it.
In Tony Hawk's Pro Skater 4, the Carnival stage has a haunted house with rails on the ground nearby. Grinding the rails causes you to go (apparently through a solid wall) into a small area with creepy noises and faces everywhere, unavoidably sliding down the tongue of what looks like a giant red demonic mask. This is not mentioned anywhere else in the game.
Tony Hawk's Underground had a similar experience to the one above in the Hawaii stage. There is a tiki statue standing outside of a store, which is perfectly fine, as the store is called "Tiki Trading Company". But jump into the mouth of the statue and you are transported into some sort of volcanic vortex world with a giant tiki statue in the center, complete with an ominous, demonic laughter. As soon as you touch any of the lava it registers as a bail and you are transported out. It is never mentioned in story, and it's only point is to unlock the Classic Venice stage from Tony Hawk's Pro Skater 2.
Tony Hawk's Underground 2 has one in the New Orleans level. By riding around on some crypts, you can turn the level from a street carnival party, to a zombie apocalypse. It can then be undone by doing a christ-air over a Jesus statue. Unlike other events possible in this game (such as getting abducted by aliens), this one is actually part of the games plot, a realistic contest between two teams over who can cause the most destruction. Oddly enough, in spite of causing an apocalypse, your team is still losing at the end of that level.
Kingdom of Loathing is pretty bizarre and intentionally inconsistent in general, but a certain Easter Egg stands out. The Sorceress's Tower is filled with overpowered enemies and difficult puzzles, one of which involves putting different kinds of keys in a door. If you happen to have a balloon monkey, you can somehow cram it in the lock (it's a Balloon-Mon Key) to meet "Unexplained Jamaican Man," who gives you a balloon ("Hey, mon. How about a balloon, mon?") and, true to his name, is never mentioned again or explained, by himself or anyone else.
The original version of La-Mulana has a secret area based on Maze of Galious (the game that inspire La-Mulana). Instead of fighting the boss of the area, he just talks to you (and I do mean the player). It's as odd as it sounds.
Mystical Ninja Starring Goemon is a pretty out there game to begin with considering the fact that the villains are aliens who want to turn the entire world into a stage. But the biggest BLAM moment happens near the end of the game when the heroes finally manage to confront the villains, Dancin and Lilly, face to face (prior to that they had only been appearing as holograms). Instead of a heated boss battles the Dancin and Lilly put on a stage performance called Gorgeous My Stage. This, while being in character with Dancin and Lilly, progresses the story in no way and of course isn't mentioned afterwards. After their performance the villains set off a time bomb and run away leaving the heroes to chase them in their giant mech. The closest relevance it could possibly have is that they used the time where the Heroes were dumbstruck to escape, even though they could have just not had the performance and escaped...
The Secret of Monkey Island has a fight scene during the Test of Thievery where Guybrush automatically interacts with objects offscreen including a yak and a heavily armed clown. He also picks up items he could not normally pick up and performs actions that are not available to the player.
In Paper Mario: Sticker Star, there's an area where you can see a goat on a distant mountain. Hit the tree in the area a few times, and a spotlight will turn on, a swing will drop down, and Birdo will slide down the rope, sit on the swing, and recite some poetry as it swings back and forth, bringing the goat (statue) to the foreground.
A literal one in Yoshi's Story at the end of level 3-4: Frustration. It's a snow-capped mountain level that despite the name is actually easy, but at the end you're inside of a boiler room fighting Don Bongo, a big lipped biped alligator whom rains down pots and pans. You have to hit his lips three times to win. The boss as well as the setting have nothing to do with that level or any levels in the game, and it's never mentioned again. One LPer suggested that the level being called Frustration has nothing to do with the difficulty (or lack thereof) but the frustration you experience trying to figure out how the boss fight ties in with the level.
In McPixel the solution to a stage based on the Bowser fights from the original Super Mario Bros. is... weird, to say the least. Giving the 1-Up to Mario turns causes him to shrink... then turn into some abstract painting, whereupon his neck stretches out, and turns the Teenage Mutant Ninja Turtle representing Bowser into... something else. Mushroom Samba, taken a bit too literally.
There is also one Bonus Round that deliberately mimics the effects of a glitch.
OFF has a couple, which even in a weird game like this one manage to stand out:
The whales that sometimes pop up in normal encounters in zone 2. No, not a ghostly or ghoulish whale. Just a regular ol' whale that found its way up a tower.
One random fish that'll jump when you step on a certain place, and never show up again, in zone 1. Easy to miss.
Zone 3 has a regular hallway with some doors on the way in. On the way out (while chased by the zone's boss), it''s completely blank and white, and no doors open.
If your character in Vampire: The Masquerade – Bloodlines is a Malkavian, you have the opportunity to experience many BLAM s. Especially memorable is an argument with a 'Stop!' sign.
Teenagent has a part where you open a refrigerator, only to find inside an Eskimo who tells you to scram. The protagonist closes the fridge and remarks that he must've gone insane. Next time you open the refrigerator, it's got perfectly ordinary food-stocked shelves inside, and the Eskimo is never seen or mentioned again.
Batman Doom has the Super-Secret level. In the middle of chasing a crook around Gotham, Batman comes upon a weird-looking portal in the floor. As he steps in, he is taken to a fleshy island floating in the middle of a black void, where he fights flying eyes that shoot batarangs at him, and then, to find the portal back home, he enters a giant mountain of meat through a tooth-filled mouth. The game then continues as normal. What.
Shogo: Mobile Armor Division: In the middle of his journey through the city of Meritropa, with the fate of the world hanging in the balance, Sanjuro is forced to make a detour to rescue an old lady's cat. It Makes Just as Much Sense in Context, and apart from the cat's squeaky toy continuing to take up the #8 weapon slot when Sanjuro's on foot the event is never referred to again. Granted, the game is an Homage to giant robot anime, and the goofier series do this kind of thing a lot.
Final Fantasy VI: The Phantom Forest/Train (and Sabin's scenario in general). Sabin and co. find themselves wandering a dark forest full of ghosts, and then proceed to ride a creepy train that ferries the souls of the departed to the afterlife only to realize they don't in fact want to go there, and proceed to suplex the hell out of the train itself to get it to stop and let them go. The forest is never mentioned again, and disappears entirely when Kefka destroys the world.
Some of the bosses feel like this too. The Tentacles in Figaro Castle? Flame Eater in the burning house? The piranhas and Rizopas Sabin and Cyan fight while falling down a waterfall?
The infamous Zap Dramatic has several of these in his games.
Ambition has a few of these.
Before Angie tells Yale that she's pregnant with his child, Yale inexplicably throws a pencil in the air. It rotates like a helicopter blade while a drum-roll plays in the background. Angie catches the pencil, and Yale compliments her catch and then grins sheepishly. There was no reason for any of this to happen.
In episode 3, we have Ted's face inexplicably superimposed over Bridget's. Apparently, it's supposed to tie into Ted's philosophy that the truth is like an onion, but it just comes out of nowhere and is never referenced in the game.
Helen's pastries in episode 9.
Whenever Duke kills you in Episode 10, he's accompanied by a green light. This is never explained at any point in the episode.
In the "Raise" episode of Negotiator, the mouse on Rolf Klink's desk will talk to you. And it tells you that there's a woman stripping behind you. And there is a woman stripping behind you. And then the cop materializes from thin air and arrests you for no apparent reason. Another version replaces the stripping woman with a suitcase full of cash that teleports away from your cursor when you try to steal it. It may be more family-friendly this way, but still, when did a susceptibility to hallucinations enter the story?
In Sir Basil Pike Public School, agreeing to "rock" with Janina inexplicably triggers a sequence which rivals Ted's dream sequence from earlier in terms of coming out of absolutely nowhere, and looking like a drug trip. It's an even bigger BLAM if the player chooses to play as a girl. Apparently due to an error on the creator's part, Janina doesn't tell you about going to record her song if you're a girl and certain other conditions weren't met. As a boy, it at least sort of makes sense in context, but as a girl it can literally come completely out of nowhere. Sometimes, you'll be sent through a weird time portal if you fail in Sir Basil Pike, with no explanation as to how or why it happens, or why it happens sometimes but not others.
In one early version of "Customer Service", if the player defends the other customer by launching into a rant against the store, Lola will not only warn the player about acting like a pig, but she will also summon a knife-wielding shadow by firing off a gray-scale photo-negative of her face. Then if the player claims to have a lawyer brother who will sue the store, the shadowy shape returns and slashes the word "IDIOT" into the screen. It must have been removed for being too frighteningly random even for a ZapDramatic game, but it could also be argued to have been the most interesting part.
In the game "Star Trek Elite Force 2," there is a part where you can find a pipe that you can jump into. This transports you from the FPS style you've been using into a Mario Homage Platformer. Once you exit, you're back where you started.
In Mario Paint, the exercise scene. After the title screen, the game plays a short, black-and-white animation of sit-ups and a handstand, while the crowd cheers. Brental Floss used this scene in a video with the comment, "Seriously, wtf was this about? Seriously."
The Grizz battle in Sly Cooper: Thieves In Time. The entire chapter he's been toted as a black gangster artist grizzly bear but when you face off against him he, completely out of nowhere, starts ranting about how he always wanted to be a skater, and starts skating around the arena shooting ice at you and forcing you into rhythm-game-style skating matches. Murray is every bit as confused as you are.
The Longest Journey has the defeat of Roper Klacks. You hand him an ordinary calculator, he pushes a few buttons, and he's somehow sucked into it. No explanation for why or how it happens. He returns as a reformed man in the sequel, and the strange anomaly is still never explained.
When Michael gets drugged and robbed by his own son, he undergoes a Mushroom Samba that involves spaceships, aliens and flying through a city of rainbows in his underwear that just has to be seen to be believed.
Two more Mushroom Samba levels follow that one. The other two involve Michael and Trevor smoking some very potent weed and being forced to battle aliens and clowns, respectively.
Trevor's final rampage missions. He is attacked by hordes of gun-wielding hipsters who drive to the battle in electric cars and scooters, and die while saying things like "I was trying to finish my screenplay."
The opening cutscene of the "Blitz Play" mission. In the middle of this almost completely serious dialogue, when Steve mentions that "some parts of the government might be corrupt," all three Player Characters, in perfect unison, make frivolous "see no evil, hear no evil, speak no evil" gestures.
Something Else: If Luigi has the Athletic Peach in Darkave, he can reach an area similar to the beginning area and enter the pipe. It leads to an edit of the Testing Area Dummied Out in the original Super Mario World. At the end, there's a pipe that leads to a bizarre area filled with Triangular Blocks and falling Green Apples. The Key use sound repeatedly plays over and over again in this section. In one of the doors, Luigi can fruitlessly pursue a Moon until a pity 1-up Mushroom shows up. Luigi can enter another door and get sent back to the entrance area. This strange level is never mentioned in context at all.
In general, any poorlydone puzzle in an Adventure Game. Some players who are more interested in the story feel this way about puzzles in general.
The entire scene and boss fight involving Benny in Comic Jumper, made even more jarring by the fact that Smiley is supposed to be in a parody of Silver Age comics, and along comes this walking, talking Total Recall (1990) reference.