A number of the What Ifs are hilarious due to the completely insane, but perfectly logical, conclusions (and, sometimes, the sheer insanity of what is being logically considered in the first place). Others are hilarious for the irrelevant but amusing tangents the author sometimes goes off on.
* [[http://what-if.xkcd.com/1/ Relativistic Baseball]]. A question about pitching [[spoiler: nukes a city]].
** of course, in that case, the question wasn't exactly straightforward. Still, the conclusion, in context, is arguably one of the funniest things on the site; [[spoiler: A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered "hit by pitch", and would be eligible to advance to first base.]]
* [[http://what-if.xkcd.com/4/ A Mole of Moles]]. No insane ending, but it nevertheless involves [[spoiler: a moon-sized ball of meat and fur that periodically erupts in plumes of boiling guts]].
* [[http://what-if.xkcd.com/6/ Glass Half Empty]]. The standard optimist-or-pessimist question [[spoiler: leaves people with shards of broken glass embedded in their faces]].
** "Free glass!"
* [[http://what-if.xkcd.com/8/ Everybody Jump]]. A rather simple question of kinematics becomes [[spoiler: [[ApocalypseHow a dire civilisation-ending catastrophe]].]]
* [[http://what-if.xkcd.com/10/ Cassini]]. A detailed and thoughtful exploration of climatic interactions concludes with [[spoiler: ''Radio/APrairieHomeCompanion'' being attacked by fire ants and alligators]].
* [[http://what-if.xkcd.com/12/ Raindrop]] features some absolutely brilliant bits of wordplay, one in each of the last two paragraphs:
--> Fear reigns supreme as the world fears rain supreme.
--> ...and the unexplained meteorological phenomenon is simply dubbed a “Skrillex Storm”—because, in the words of one researcher, “It had one hell of a drop.” (The book changed this to "dubstep storm".)
* [[http://what-if.xkcd.com/13/ Laser Pointer]]. A question on light ends with [[spoiler: the moon becoming a rocket engine and Earth suffering a Class 4 Planetary ApocalypseHow.]]
* [[http://what-if.xkcd.com/19/ Tie Vote]]. A question about elections ends with this gem, with an image to match:
-->...when one of the Florida electors reaches into the hat to draw a name, [[spoiler:he or she is struck by a falling cocaine bale, the hat is hurled away within the next few seconds by a tornado, and the elector is obliterated minutes later by a meteorite impact.]]
* [[http://what-if.xkcd.com/21/ "Machine Gun Jetpack":]]
--> ''(Stick figure has attached a rear-facing [[GatlingGood GAU-8 Avenger]] to the top of a car.)''
--> '''Cop:''' Do you know why I pulled you over?\\
'''Stick:''' No.\\
'''AltText:''' actually, what i'm confused about is 'how'.
* In [[http://what-if.xkcd.com/23/ "Short Answer Section II"]], Cueball has a hypothetical printer that can ''literally'' print a sheet of money once every minute. So, now he's trying to figure out what the annual income of that is.
--> "Let's see...$400 per minute...and there are ''[[EarWorm 525,600 minutes in a year]]''...dammit [[{{Theatre/Rent}} RENT]]!
* [[http://what-if.xkcd.com/24/ Model Rockets]]'s punchline is a CallBack to [[http://xkcd.com/1133/ Up Goer Five]].
* [[http://what-if.xkcd.com/30/ Interplanetary Cessna]]:
** The description of how well a plane would fly on [[DeathWorld Venus]]:
-->The upshot is: Your plane would fly pretty well, [[YesExceptNo except]] it would be on fire the whole time, and then it would [[FromBadToWorse stop flying]], and then [[CriticalExistenceFailure stop being a plane]].
* [[http://what-if.xkcd.com/42/ Longest Sunset]] kicks off the article by defining what qualifies as a sunset and what doesn't. Examples of the latter include the sun crossing the horizon partway and then reversing direction, the sun ''splitting in two'' and half of it setting, the sun ''landing on the horizon and hatching like an egg'' (AltText: "you bred sun-raptors?"), and a ''square sun'' that doesn't get a chance to do anything before the narration cuts it off (AltText: "aww, man, you didn't even let me try").
* [[http://what-if.xkcd.com/43/ Train Loop]] discusses jet-engine-powered trains.
-->Sadly, they never took off. Fortunately, they never took off.
** "Ok, putting the jet engine on top didn't work. Maybe we should try something different." So he puts the jet engine on the bottom, so the train can't make contact with the tracks and tips over.
-->...why did we think that would work? Forget that idea.
* This excerpt from [[http://what-if.xkcd.com/47/ Alien Astronomers]]: "The Sun is really bright[''[[http://www.google.com/search?q=site:craigslist.org+chevrolet+citation citation needed]]''] and its light illuminates the Earth.[''[[http://en.wikipedia.org/wiki/Citation_(horse) citation needed]]'']" Funny enough by itself, but then you check the links...
** Another one links to the Wikipedia page for [[http://en.wikipedia.org/wiki/Cetacean Cetacean]].
* [[http://what-if.xkcd.com/49/ Sunless Earth]]. After a long list of the surprising benefits of a lack of sunlight, the ending bluntly points out [[spoiler:we'd end up freezing to death.]]
-->It's the Sun. We need the Sun.
* [[http://what-if.xkcd.com/53/ Drain the Oceans]]. Sure, the oceans would be gone and with them most of the biosphere and planetary habitability, but the real major change is [[spoiler: The Netherlands conquering the planet.]]
** In [[http://what-if.xkcd.com/54/ Drain the Oceans: Part II]], after the ocean is finished being deposited at Mars, [[spoiler:the Netherlands use the ocean-draining portal to conquer Mars as well]].
* [[http://what-if.xkcd.com/57/ Dropping a Mountain]] calls back to Drain the Oceans. [[spoiler: The mountain is dropped from high enough that it pulls an orbital slingshot around the Earth, and crashes into New Netherlands, the now-Dutch-and-watery Mars]].
* At some point, Munroe started getting creative with his citations. Clicking the numbers in [[http://what-if.xkcd.com/55/ Random Sneeze Call]] reveals these gems:
-->However, given that sneezes are far more common than murders,[[labelnote:2]]Citation: You are alive.[[/labelnote]] (...)
-->[The control group] was given no allergens at all; they just sat alone in a room for a total of 176 20-minute sessions.[[labelnote:5]]For context, that's 490 repititions of the song Hey Jude.[[/labelnote]]
-->The subjects in the control group sneezed four times during those 58 or so hours,[[labelnote:6]]Over 58 hours of research, four sneezes were the most interesting data points. I might've taken the 490 Hey Judes.[[/labelnote]] which (...)
** And again in [[http://what-if.xkcd.com/58/ Orbital Speed]]:
--->The X-15 aircraft reached space just by going fast and then steering up.[[labelnote:3]]Make sure to remember to steer up and not down, or you will have a bad time.[[/labelnote]]
--->The ISS moves so quickly that if you fired a rifle bullet from one end of a football field,[[labelnote:7]]Either kind.[[/labelnote]] the International Space Station could cross the length of the field before the bullet traveled 10 yards.[[labelnote:8]]This type of play is legal in Australian rules football.[[/labelnote]]
* When doing the research for [[http://what-if.xkcd.com/62/ Falling With Helium]], Randall made so many requests to Website/WolframAlpha that he got ''his IP address banned''. The image of his ban-appeal request is icing on the cake.
-->'''''Please provide us with detailed information about what you were trying to do (e.g. type of project, query types, etc.):'''''
-->''Calculating how many rental helium tanks you'd have to carry with you in order to inflate a balloon large enough to act as a parachute and slow your fall from a jet aircraft.''
* [[http://what-if.xkcd.com/74/ Soda Planet]] concludes with a diagram of a person drinking directly out of an apatosaurus. With a straw.
* [[http://what-if.xkcd.com/83/ Star Sand]] is relatively tame by ''What If'' standards, but the final image's alt text is amusing: "[[Webcomic/XkcdTime Just to be clear, this image does not update every hour.]]"
** Another image describes increasingly large stars as "stars that are heavier, bigger, bluer, younger, (the rest is crossed out) [[Music/DaftPunk harder, better, faster, stronger]]". These are referred to as "Daft Punk stars" in the main text afterwards.
* Citation #5 in [[http://what-if.xkcd.com/84/ Paint the Earth]] goes off on a tangent listing things that are not buildings.
-->EXAMPLES OF THINGS THAT ARE NOT BUILDINGS: Ducks, M&Ms, cars, the Sun, cuttlefish, microchips, Macklemore, lightning, goat blood, zeppelins, tapeworms, pickle jars, those sticks you use to toast marshmallows, alligators, tuning forks, minotaurs, Perseid meteors, ballots, crude oil, sponsored tweets, and catapults that throw handfuls of engagement rings.
* [[http://what-if.xkcd.com/85/ Rocket Golf]]:
** The 237 mph diagram, comparing two circles of nearly equal size: "Bag Full of Golf Balls", and Earth ... which is labelled "Ball Covered With Golf Courses."
* [[http://what-if.xkcd.com/77/ Growth Rate]] states that if children kept growing at the rate they do just after birth, they would be as tall as Darth Vader by the time they were three. Then there is a picture of Dark Vader and a three-year-old that's caught a beetle.
--> '''AltText:''' I find the bug you found disturbing.
* [[http://what-if.xkcd.com/92/ One-Second Day]] starts off with this absolute gem:
--> "The Earth rotates,[[[http://www.timecube.com/ Citation Needed]]] which means its midsection is being flung outward by centrifugal force. [[labelnote:1]]Which is still a [[http://xkcd.com/123/ real thing]].[[/labelnote]] This centrifugal force isn't strong enough to overcome gravity and tear the earth apart, but it's enough to flatten the earth slightly and make it so you weight almost a pound less at the Equator than you do at the poles. [[labelnote:2]]This is due to several effects, including centrifugal force, the flattened shape of the earth, and [[ArsonMurderAndJaywalking the fact that]] if you go [[CanadaEh far enough toward the pole in North America]] people start offering you poutine.[[/labelnote]]
* [[https://what-if.xkcd.com/94/ Billion-Story Building]], in which Randall attempts to explain to a four-year-old why building a billion-story building is impossible. It's quite hilarious, because you can tell he's making a genuine effort to let the young girl asking the question down gently, but what makes it even funnier is the utter ''absurdity'' of such a building once Randall draws a billion-story-tall skyscraper and compares its size with Earth (It's tall. ''Really'' tall. Like "reaches-past-the-Moon" tall.)
* In "[[https://what-if.xkcd.com/103/ Vanishing Water]]", Randall is asked what would happen if all the oceans and lakes on Earth were to instantly disappear. In the AltText of one of the pictures, he grumbles that this would cause yet ''another'' situation where all life on Earth would die horribly.
-->''"Why can't the questions ever be, like, 'what if I saw a really good movie' or 'what if I adopted a puppy'?"''
* In "[[http://what-if.xkcd.com/104/ Global Snow]]" a small duck pond full of an inch worth of water made into snow is shown shrinking due to it's own weight with a small duck in winter gear sitting on top waiting for it to become a pond again.
--> ''[[AltText "I am a patient duck."]]''
* A hilarious aside near the beginning of [[http://what-if.xkcd.com/112/ Balloon Car]], asked by a Cambridge father on behalf of his 12-year-old daughter:
-->Thanks for getting your dad to send in this question! He said not to worry about the "legal and insurance difficulties," so I think it's safe to assume he's taken care of all that.
-->''Note to police: If you've recently taken into custody two unidentified underage drivers, a stolen Ferrari, and a bunch of helium balloons, the person you're looking for is '''Phil Rodgers''' in '''Cambridge, UK.'''''
* Some of the questions go unanswered in the "Weird and Worrying Questions" segments. Such as "Is it possible to drop your teeth's temperature so they shatter when drinking a cup of coffee?"
--> Thank you for my new recurring nightmare.
:: "How many houses catch fire every year in the U.S. and what would the best way to increase that amount by fifteen percent?"
--> Hello, police? See, I have a website where people ask questions...
:: or "Can you cry so much you get dehydrated?" by someone called Karl:
--> ...Karl, is everything OK?
:: or "Assuming a relatively uniform resonant frequency in a passenger jet, how many cats, meowing at what resonant frequency of said jet, would be required to "bring it down"?" asked by someone named Brittany:
--> Hello, FAA? Is there a "Brittany" on the no-fly list? ...Yes, with cats. That sounds like her. Ok, just making sure you were aware.
* Seeing as it's sealed tight to operate under the sea, could a submarine and its crew operate in space? This situation comes up while thinking about it:
--> '''Sonarman:''' Captain, according to sonar, we're re-entering the atmosphere! \\
'''Captain:''' No part of this makes sense.
* This gem from [[http://what-if.xkcd.com/124/ Lunar Swimming]]:
--> Swimming underwater would also feel pretty similar. The inertia of the water is the main source of drag when swimming, and inertia is a property of matter[[labelnote:1]]♬ BILL NYE THE SCIENCE GUY ♬[[/labelnote]] independent of gravity.
** The same page also indicates that Munroe "nerd-sniped [him]self trying to figure out whether it'd be possible to do a Slip N' Slide loop-the-loop on the Moon".
* In "[[http://what-if.xkcd.com/126/ Stairs]]" the time and effort required to reach the top of really high stairs is measured in butter. With the note that alternatively one can just ride a motorcycle upstairs. It also talks about the time it would take a slinky to get down from those stairs ... and the result is also given in butter.


* "What If...No One Was Watching the Watcher?" us an issue that takes a break from the normally serious core concept of the series and instead just makes up ridiculously goofy shit. Even the front cover! It's literally Uatu the Watcher in MarilynMonroe's "blown skirt" pose.
** One What If: "What If ThePunisher Was the Stern But Fatherly Type?" This turns the normally trigger-happy crim-killer Frank Castle into a hilariously stereotypical strict teacher who forces DoctorDoom to sit in a corner and think about what he's done and makes {{Galactus}} write "I Will Not Eat Inhabited Planets" 500 times on a blackboard no bigger than Galactus' foot, forcing the world eater to get down on all fours to write on it!
** "What If Thanos Turned Galactus into a Human Being?" is the central story of the issue. Rather than kill him as he attempted to, Thanos subjects Galactus to the worst possible punishment...being turned into a human being! And not just any human, but ElvisPresley! Not just a good lookalike, but the King himself! Cue Galactus Presley being taken in by a kindly Elvis fan and making it big as the King himself on a comeback tour until Adam Warlock tells him who he really is and his role in the universal balance. Cue Galactus...deciding to stay as Elvis. Even Uatu's having fun nonetheless, grinning as he attends one of Galactus Presley's concert tours.
-->'''Uatu:''' I maybe the Watcher, but right now, I'd prefer to be the Listener!