Lothar: That's rarely a good sign.
So the hero has stormed the Big Bad's lair, taken care of his Mooks, and disabled the Doomsday Device. Approaching the cowering villain, he raises his weapon of choice to deliver the Coup de Grâce... and the villain starts laughing. The hero will commonly ask, "What's so funny?", whereupon the full extent of his foe's nefarious scheme will be revealed.
Perhaps it is a case of I Am Not Left-Handed, or maybe the villain has some sort of Dead Man's Switch which will blow up the lair if he is killed. Often he will reveal that his death is just the beginning, or that his demise will not further the hero's cause for some other reason.
There are three common responses to such a moment. One is that the situation is totally reversed, and the hero is defeated (common when the villain has some weapon or ability he has been keeping secret). The second is that he has to prevent himself from dealing the finishing blow to deal with a new threat (maybe his Love Interest is caught in a Death Trap which will activate upon the death of the villain). In the third, he kills the villain anyway in the knowledge that the real battle is yet to start.
Frequently inverted in that it might be the hero who looks on the verge of defeat before revealing that they expected this all along, in which case a Big Damn Heroes moment is common.
Literal laughter is not actually necessary for it to be this trope, just any kind of expression dissonant with the situation at hand. Will often overlap with Laughing Mad, Evil Laugh, Xanatos Gambit, "The Reason You Suck" Speech. May immediately precede The Reveal. Almost always a Plot Twist.
- Happens quite a bit in Asterix; thanks to their Magic Potion giving Super Strength, the Gauls of Asterix' village are always quite eager to get into scraps with the Roman Legions, and so those not familiar with the Indomitable Gauls are always concerned when their opponents start snickering before a battle. In "Asterix And The Big Fight", the Romans prepare to attack the Gauls because they believe Getafix the druid has been rendered an invalid, and thus, no Magic Potion. Their confidence quickly dips when they see the Gauls laughing.
Legionary: O Centurion, we don't want to be awkward, but every time we attack these savages, they start laughing and make mincemeat of us...
- In Captain America: Civil War, when Everett Ross asks Helmut Zemo how it feels to see his plan fail so miserably, Zemo smiles and asks, "Did it?". The implication is that the existence of the Accords and the rift between Iron Man and Captain America means Zemo has won. Of course, he hasn't... but someone else has.
- Indiana Jones and the Temple of Doom. Early in the movie Indiana Jones confronts the villainous Lao Che. After Indy takes a drink, Lao Che makes a demand.
Lao Che: And now, you give me the diamond.
Indy: Are you trying to develop a sense of humor, or am I going deaf?
Lao Che: [holds up a vial]
Indy: What's that?
Lao Che: Antidote.
Indy: To what?
Lao Che: [starts laughing] The poison you just drank, Dr. Jones.
- Predator. After Dutch incapacitates the title creature, it activates a device on its wrist and starts laughing at him. Dutch realizes the device is a Self-Destruct Mechanism and starts running...
- The Princess Bride. Happens during the trope-naming scene for I Am Not Left-Handed.
Inigo: I admit it: you are better than I am!
Man in Black: Then why are you smiling?
Inigo: Because I know something you don't know.
- In Total Recall (1990), Richter's forces riddle Quaid with bullets. Then the latter gets up and starts laughing loud to the shock of his opponents. Turns out the Quaid they shot was just a projection.
- In the second Jack Blank book, The Secret War, the heroes successfully stop Speedrazor and his cohorts from attacking a train. While they are discussing their distrust of the Secreteers, Speedrazor laughs uproariously but is spitefully knocked out before he can divulge anything. Later on, it is revealed after interrogating Speedrazor more than half the book later that they were sent to destroy the train by a Secreteer, Obscuro, who had undergone a FaceHeel Turn.
- Cheers: When it appears that Harry the Hat has conned Coach, Sam, Norm, Cliff, and another conman out of a bunch of money (including Coach's life savings) Coach has his head in his hands, shaking. Then it turns out that he's not crying, he's laughing. "Coach, what are you laughing at?" Coach responds "That!" and points to the back of the bar, where Harry reappears. He and Coach set up a con within a con within a con in order to con the other con artist out of his money.
- Played for Laughs in the first paintball episode of Community, where Chang opens his jacket to reveal a paint bomb after being tagged by Jeff.
- Doctor Who: A heroic example is Martha's sniggering in "Last of the Time Lords" while she kneels before the Master who's all posed to murder her in front of (nearly) everyone she holds dear. He naturally asks what's so funny, and she proceeds to explain just how Out-Gambitted he really is.
- In Star Trek: The Next Generation, young Picard starts to laugh, seemingly without any reason, after a Nausicaan has stabbed his heart. Picard survives, but his heart has to be replaced by an artificial one. Many years later, this artificial heart brings Picard into a potentially lethal situation, and in what may or may not be limbo, Q offers Picard the bargain that he will live if he goes back in time (replacing his younger self) and prevents the situation that got him the artificial heart in the first place. Picard does just that, but discovers that this has steered his live into a completely different path—an unbearably boring one. After Picard has learned his lesson about not regretting your past choices, Q allows him to go back in time once again and restore the original timeline. And this time, Picard actually has a reason to laugh when he gets stabbed.
- VR Troopers: This is the reaction of some monsters who No-Sell the standard finishing move.
- Electrobot laughed when the laser lance impaled him but fell off of his perch, when he realized what had happened he got up, PISSED, but was quickly cooled off by the finishing move.
- Mechanoid laughed off the VR Double Team and the laser lance impalement and finisher at first. Subverted when more power was used resulting in him shouting "Woah! Woah! Woah!" over and over again in surprise.
- Fanbot was unharmed by everything in the book, the double team, the laser lance (the impalement and slashing), at most distracting him briefly enough to allow Kaitlin to escape to safety. The VR Technobazooka, otherwise reserved for aerial assaults, was required to finish the job.
- Luann: In the strips for January 8th and January 9th 2013, T.J. grins at Ann Eiffel before telling her that her incriminating admissions (which she thought she had erased) had been backed up elsewhere.
- An old joke among tabletop gamers are variants on "When the DM is smiling, you should start worrying."
- Crash Bandicoot 3: Warped: In the cutscene you get after you step onto Neo Cortex's boss-stage button, Cortex and Uka Uka meet you in the warp hole, and Cortex . . . laughs. He says this was the part where he's supposed to be angry with you, but ...
Uka Uka: Now that you've gathered all the crystals, all we have to do . . . is take them from you!
- In the Injustice 2 story mode, Green Arrow and Black Canary infiltrate Gorilla City, overpower Grodd's allies, and then defeat and cuff Grodd himself...at which point Grodd starts laughing, which Green Arrow notes is never a good sign. Cue Brainiac's spaceship appearing in the sky.
- Some Phoenix Wright: Ace Attorney trials go this way. Prove something important and the prosecution will be smiling afterwards. It either means A) that you just screwed yourself over, B) that they already knew this and was toying with you or C) that they still have to reveal their best evidence.
- Exterminatus Now: After raiding Morth's stronghold, killing his cultists, messing up his daemon-summoning ritual (it summoned a different one), Eastwood shoots Morth half a dozen times after he injects himself with daemonic ichor. Eastwood is all ready to leave, until Rogue points out Morth's body is laughing, right before he ascends to daemon princehood.
- The Order of the Stick:
- Lampshaded in #810: Nale and Sabine have Durkon at their mercy, and Nale notices a smile on Durkon's face in spite of Nale's apparent victory. He fails miserably in an attempt to defy the trope by noting that since he knows what Durkon is up to, he is in a better position to counter it. Eventually it turns out that Durkon is expecting to meet Malack, a powerful cleric with a grudge against Nale, who promptly enters the scene and almost kills Nale in the ensuing turn.
- A lesser example is when an evil druid has protected his treants against every form of damage except sonic. When Durkon summons the mother of all thunderbolts four miles out to sea, the druid tells them not to panic as the lightning lights up the area, not seeing Vaarsuvius smiling wanly. Four seconds later, we get to see why.
- In Invader Zim, when Zim breaks up with Tak, she starts laughing uproariously before she reveals her Irken appearance.
- In Ninjago, General Kozu, who been captured in Ninjago City, does this when a portal (ostensibly one created by the world's heroes) appears. Moments later, his boss, the Overlord, lands in Ninjago City and turns everyone in the city evil, effectively taking over the world within minutes.