Lois wistfully looking on as her whole family (whom she ran away from after they admit they blew her birthday present money on candy) brawls with a group of clowns + Kenny Rogers' "You Decorated My Life" = pure distilled hilarity.
On the season one episode "Home Alone 4," Francis invites his hoodlum friends over on the condition that they don't invite other people and have a party at his house. One Gilligan Cut later, we find the house trash and immediately assume that Francis' friends broke the promise. It turns out Francis' friends are so destructive that it only takes three of them to trash an entire house. It was so bad that all three of Francis' friends got arrested.
Malcolm spends the Cold Opener scraping the most disgusting things off the floor, the garage, and the back of the fridge onto a sandwich. Then he finally sits down to eat it and Reese immediately swoops in to steal it and take the first bite, just as Malcolm planned.
Surreal performance piece by Dewey and babysitter (played by Bea Arthur)—to the tune of ''ABBa's "Fernando" (ending with the eccentric grandmotherly woman having a stroke or a heart attack and being carted away by the paramedics). Now a "Funny Aneurysm" Moment thanks to Bea Arthur's death.
On the episode where Lois gets fired from her job at Lucky Aide because the store manager wouldn't take back the bottle of cognac Dewey accidentally shoplifted, Malcolm's family gets some food donations from the neighbors. Lois doesn't like it, commenting on how food donations are always bad. Hal doesn't believe her and asks anyone if they want some olives he found in a can. Lois's response: "Those aren't olives; those are peaches!"
As a nice little bonus: After Hal is hospitalized, he lets out a huge fart. Malcolm then awkwardly tells his brothers that "The first one to laugh gets their ass kicked".
The episode where Francis has to visit Ida during Christmas. There's a moment where Francis begins to mocks her with a Christmas song from a card he bought her. This causes her to stab him in the leg with a knitting needle.
And the follow-up where Francis leaves a whole army of these cards in her house after he left, causing her to go insane trying to tear up each one that begins its chime.
Grandma Ida: You do this to torture me? To hurt me?
Francis: You don't like Christmas music?
Grandma Ida: It sounds like the song they sang when they would run through the villages and throw the babies into the fire!
The montage when Hal, Dewey, and Reese decided to have fun with the wood chipper. They throw in plushies, watermelons, backpacks, all sorts of stuff, until finally, they walk up with a box of confetti and throw it in the wood chipper. Hal says, "...Obviously, we've run out of ideas."
When Francis gets dumped by his "sweetheart" who he had ditched military school to be with, he lies down in the woods and cries out in anguish. By itself, it wouldn't be funny, but then Dewey hears his agonized bellowing from the darkness and starts throwing rocks at him, mistaking him for a monster. And then it's freakin' hilarious.
In the season two episode "Malcolm Vs. Reese" Francis got two tickets to a wrestling match, so he made Malcolm and Reese do favors and other stuff to see who loves him more. All of it is funny, but the funniest part was when he made both of them do The Happy Dance.
Francis: Come on guys, it's Rage in The Cage, you should be happy!
Reese: ...We are happy.
Francis: ...Well, you're not doing the happy dance...
Malcolm and Reese: Happy dance, happy dance, we love to do the happy dance...
Malcolm and Reese: Happy dance, happy dance, we love to do the happy dance.
Malcolm and Reese:HAPPY DANCE, HAPPY DANCE, WE LOVE TO DO THE HAPPY DANCE!
In the season four episode "Family Reunion" Francis was forced to spend all day with the kids, so he had enough and told them a story called "The Kids WHO COULDN'T PLAY BY THEMSELVES!".
Francis: And the the little boy about your age was found hanging in the moonlight, strangled by his own intestines, and there was just enough life in him to say... YOU'RE NEXT!
The entire A.A. episode.
The fourth season episode "Boys at the Ranch", where Malcolm, Reese, and Francis are setting off a mass of fireworks at night. As the display winds down, Reese asks "How do we know which one's the Komodo 3000?" His question is answered a second later with a fireworks explosion so bright, it turns night into day for about five seconds.
Francis (deafly yelling): DID IT SAY WHEN OUR VISION WOULD COME BACK?
When Lois is pregnant, she tries to avoid ballooning up per her doctor's orders. But Hal has just realized that he's a fat admirer, so he sabotages her diet attempts and secretly fattens her up instead. He stirs chocolate syrup into her tea and, when she buys celery, fries it in bacon grease. An hour later, she sits at the kitchen table telling him about how she's actually gained despite her diet, then stops and looks at the celery. Beat. Then she keeps chewing, telling him "My hormones are so screwed up! This celery tastes like bacon!"
Malcolm comes to the couch with two sodas, and Reese goes through a I Know You Know I Know trying to figure out which one he shook up. Eventually he decides to just get a soda from the fridge...which promptly explodes on him.
Hal and some other dads are in a class for bonding with their babies. After the instructor leaves they start having competitions involving the babies, which can spit up more, which can sit up on its own the longest, etc. eventually getting to them playing shuffleboard with the babies as the disks. Lois and the rest of the family walk in at the exact time Hal is doing this. He wins, and starts gloating. One of the kids then asks Lois why she isn't yelling at him yet. Her response:
Lois: See that goofy look on his face? I want to remember that look. We're not gonna be seeing it for a long time.
Francis comes home after getting legally emancipated so he could drop out of military school, assuming that his parents will be calmly okay with it since they've had a week to absorb the news. Cue Hal chasing Francis down the street in a murderous rage.
Stevie has some great ones, but one of the best comes in an opening bit where Malcolm threatens him with a beating if he laughs at Malcolm's Shakespeare recital. Stevie's response?
"Bring it, >GASP< Homeo"
From "Stilts", Reese decides to sign up for multiple drug tests in order to make money, completely oblivious to the fact that mixing numerous, untested drugs is a bad thing. He calls Francis, completely out of his mind and hysterical, crying that he doesn't want to do drugs anymore after he did something bad. We don't know how he did it, but he apparently stole a police horse.
Reese: Francis, you've gotta help me! I don't wanna take drugs anymore!
Francis: Okay Reese, I want you to tell me, very specifically, what kind of drugs did you take?
Reese: All of them!!
Francis: Dude, didn't you learn anything from the time my friends babysat you and Richie tried to dry you off in the oven?
Meanwhile, Hal accidentally ended up spending up nearly a thousand dollars on phone sex, and to placate Lois into a calmer state when he tells her, presents her with a pair of beautiful shoes (designer knock-offs) at work. The people in the store are witnessing Hal surprise Lois with the scenes and they're all "aww, how sweet", until this happens:
Hal: I accidentally spent $800 on phone sex.
(The shoppers all suddenly shift gear with an Oh Crap look as Lois's smile still lingers)
Lois: I was doing my makeup in the rear view mirror, and I ran over your golf clubs!
Hal: I burned a hole in your favourite dress.
Lois: You didn't get that promotion because I called your boss a fatass at the Christmas party!
Hal: I lost my wedding ring three years ago! This is part of a lawnmower!
Lois: Your Aunt Lucy isn't angry with you. She's dead, I just forgot to tell you!
Even funnier when you realize that Hal's confession about burning a hole in Lois's dress is a Brick Joke: it refers back to the events of episode two, where Lois unleashed her first on-screen hell-raising bout with the boys when she thought they ruined it and found it stuffed in the toilet. The poor attempt to hide the damage reeked of something the boys would do, and they became the unfair targets of her wrath because of their poor track record (and at the end of the episode, it's implied that Hal did it, after he had a cigar and accidentally burned a couch cushion with it. This episode outright states that Hal burned the dress).
It cuts back to this:
Hal: And I purposefully dropped that bowling ball on your foot so you couldn't go to your high school reunion!
Lois: I'm two years older than you think I am!
In the same episode, Malcolm gets a Humiliation Conga. Lois gives him a job offer at the supermarket as an Uncle Sam mascot on giant stilts (which she guilt-trips him into taking), about as demeaning and ego-wounding as he could dread. This is also to replace their current mascot (played by Tim Stack), who keeps showing up to work skunk-drunk. Malcolm begrudgingly takes the job, which nets him a humiliating laugh-down by several teenage girls who mock his totally undignified, "would not bang" appearance. Malcolm asks Craig to help him get the old guy to shape up his act so he can take his old job back. However, the guy is a bum without a cent to his name and taking the loss of his job very personally. He was so passionate about it he's scraped together his own Uncle Sam getup from garbage.
Later on, the deposed Sam fashions stilts out of junk, shows up to confront Malcolm at the store drunk outta his gourd and kick his ass in a stilt war! Malcolm tries to run away clumsily, while sheepish Craig does his best to be the Big Damn Hero in his own gawky way, gets a dinky toy airplane from the store, planning to fly into the drunk Uncle Sam's head and knock him senseless... except when he unwraps it from the box, it requires assembly.
Craig(notices he has to screw the airplane parts together): Dammit!! What aisle are the screwdrivers in!?!
Meanwhile, Malcolm cannot afford to wait for Craig to finish the plane assembly with the drunk man catching up to him. Malcolm decides to improvise a last-resort escape by jamming the stilts into two shopping carts. He thinks they could work as roller skates, but forgets one fatal flaw- they roll in opposite directions, resulting in the ultimate groin pulling split. Then, just to make things worse, Craig shows his RC inexperience and flies the plane into Malcolm's top hat. It jams into the side and continues to spin pitifully.
Malcolm finally gives up and prays to God for salvation from drunk Sam's tirade, asking for even the most pathetic miracle. In comes Reese on the runaway police horse, still whacked out from the drugs, slouched over the saddle and sobbing like a baby. The horse smashes through Sam's stilts and sends him falling over... then storms into the supermarket and wrecks the place, cutting off Hal and Lois's argument before it reaches the point of no return. Long story short, Hal buys Lois the real pumps to shut her up, Reese is detoxed, and Malcolm troops through icepack therapy on his hideously maimed crotch.
And the original Uncle Sam? Malcolm finds him a job with the circus — working in a depressing cubicle farm run by a midget ringmaster.
In the episode "Pearl Harbour", it takes Jessica a long to time to convince Malcolm that Reese might be gay because he never suspected his actively perverted brother of hanging the other way (It Makes Sense in Context, and to be fair, he once caught Reese trying to take advantage of one of his female friends who had hit puberty and gained buxom). However, when Jessica needs to do the same to Reese...
Jessica: I didn't do it for myself, I did it for your brother.
Reese: Malcolm's gay? I knew it!
Malcolm and Reese dancing to "Take A Chance On Me". The look on Dewey's face in the reaction cut is what really clinches it.
In "New Neighbors", Reese is being stalked by their neighbors' young daughter, who enjoys biting him. It gets to the point that Reese is conspiring ways to get the family in trouble. He quickly mentions that the boy will be labeled a thief, the parents will be taken into jail and then starts an elaborate fantasy about the daugther taken away from her parents, landing in foster care, where she'll bite her foster parents so much they'll abandon her at a gas station bathroom, at which point she'll be found by hillbillies and spend the rest of her life biting them.
There's also Dewey's fear of the lawn gnome coming to life and eating him, after the neighbors' son lied to him about it. Through a number of contrived coincidences, the gnome keeps popping up around him and Dewey becomes paranoid.
Dewey: The gnome is evil! It wants to eat me!
Lois: They're all evil people, honey.
Meanwhile, the son, a master of Blatant Lies, has been getting Malcolm in trouble for no apparent reason, up to framing him as a peeping tom. When the police come by the house after Malcolm's falsely reported, Malcolm questions as to why he would bother peeping in this neighborhood since everyone's so boring. Hal counters with a slightly disturbing speech about how people peep solely for the power of invading the lives of others. The police officers look at Hal with a noticeably disturbed look when he finishes.
The bowling episode, especially when the Malcolms of both realities face the camera and say "I love/hate bowling!"
In one scenario, Malcolm keeps bowling gutter balls. Lois tells him that he is not leaving until he bowls a strike. This causes Malcolm to reach his breaking point and he angrily takes his ball and walks down the lane. He's right in front of the pins, and yells "here's your damn strike"...and then completely misses the pins when he throws the ball.
Dewey's opera, which he composed based on Lois and Hal's feud over a larger bed which turns out being Lois wanting to hide her problems with flatulence. Lois and Hal sit down along with almost everyone else they know to watch the play, and say "I just hope Dewey doesn't embarrass himself." Cue the episode ending door slam.
The Halloween episode, where the boys decide to launch a diaper off a giant slingshot. They start chanting "Diaper!" and then fire. All we get is a reaction shot as they stop chanting, and Francis says, "Uuugh! No more of those." The boys just silently nod in agreement.
Honestly, there are so many of Hal's plots — feeding his manic steamroller obsession after winning $500 on a scratch ticket, being revered as a god to a group of dim-witted bodybuilders, getting drafted into numerous corporate and extra-governmental conspiracies (often due to mistaken identity, like when he, Lois, and Dewey were stuck at the airport and he used a businessman's airport lounge card to treat himself to the good life, only to get roped into an international video conference). This would never work with any other character on any other sitcom, since Hal's just such a constant, hapless everyman victim of a world gone utterly mad.
In one episode, Malcolm and Stevie are performing an experiment to make two solutions in a test tube separate, and after Reese bounces a ball on the ceiling, they come back to find it has magically separated, when they were unable to make it happen themselves. Bewildered, they ask Reese to repeat what he did earlier to figure out how he influenced this freak occurrence. Too bad Reese has no clue, so they have to play out his entire day from the beginning. It eventually gets to a part where Reese invades their bedroom closet behind Malcolm's back, now public knowledge to both him and Stevie...
Reese(walks out of the closet with a red shirt; Malcolm and Stevie are puzzled) Then I took one of Malcolm's shirts... And then I...(Stuffs Malcolm's shirt in his pants, feeds it under hiscrotch, pulls it out from under his butt and begins flossing with it'; Malcolm's jaw drops and his face freezes with absolute horror, and Stevie's eyes bug out in repulsion; Reese yanks the defiled shirt out and hangs it back up)
Malcolm(mortified) ...OH MY GOD!!!
Reese(returns holding a hammer with a devilish grin) And then I "played" with Dewey's Game Boy.
This golden nugget of stupidity from Reese:
"I made a discovery! By mixing blue and yellow you can make an entirely new color! I'm gonna call it... Blellow!"
The episode does come with a Pet the Dog moment for Reese when he replays himself doing math homework, gets frustrated, and goes into the bathroom to call himself stupid and say "I hate you" to his own face in the mirror. Malcolm and Stevie take it to heart and give him a hopeful pep talk.
Later that episode, Malcolm and Stevie find out when Reese bounced his ball off the ceiling, it dislodged some tile grout. The grout fell into the open test tube and separated the chemicals. But what was that mystery substance? They deduce it as asbestos. As in a substance that is highly toxic for human exposure.
Malcolm & Reese(blindly celebrating their scientific breakthrough and hopping around like idiots): We have asbestos in our ceiling! We have asbestos in our ceiling!!! (beat) (it finally dawns on the brothers this is NOT a good thing; cue cut to the entire house being treated for asbestos removal)
Malcolm, evidently at the end of his tether, pressing a test tube up against his forehead, scrunching his face up in concentration and yelling "SEPARATE!" in the hopes of a miracle. It doesn't work.
Hal demolishes a beehive for the honey inside, wasting almost the entire colony of bees... but one of them was a tough S.O.B. and survived with intent for revenge. It torments Hal for days, primed to ram its stinger into his flesh, until finally, on a drive back home, the bee chases him down the road. Sure, Hal could just ignore the bug, but he instead saddles the family with more debt by totaling his car to squash the bee against a wall.
Malcolm writes a song to play on his guitar and all he ends up doing is unintentionally adding new emo lyrics to the Meow Mix jingle, which his family picks up on right away.
In "Ida's Dance", Reese bonds with Hal over horror movies while Lois is visiting her mother. Only Reese's preferred horror movies are completely over the top torture porn slasher movies with such charming titles as "They Peeled My Face." Hal is not soothed by the fact that the director went to jail for using actual corpses. Reese loves every minute of those movies but Hal is reduced to a traumatized five-year-old in the first thirty seconds of each film. We get such tidbits as this:
Man on TV: Not my eyes! Not my baby's eyes!
Later, Hal attempts to hide the TV from Reese, but ends up accidentally breaking the glass and landing on his back. He's desperately trying to keep the TV off of him as broken glass rains down on him. He's screaming at Malcolm and Dewey to help him, but they can't hear him after both have accidentally deafened the other (Malcolm tried to get Dewey to teach him to appreciate music properly for a failed class, but he drives Dewey mad to the point where he puts on headphones and ignores him, so Malcolm, in a rage, turned the volume all the way up. Then later, Dewey tries to get revenge by setting up two huge speakers around the door where Malcolm walked in and holds an airhorn to the microphone behind his back. So when he tried to give Malcolm a "reason you suck" speech while he waits in the doorway, Jamie crawls out of nowhere and accidentally(?) pressed the air horn button into the microphone.) They're calming eating dinner while Hal is trying to save himself from being blinded by jagged glass.
Hal: Save your father's eyes! Aaaaaahh!! AAAAAAAAAAHHHHHH!!!!
This isn't even taking into account the main story of Lois discovering Ida has met a group of women from the same country she is, and all of them are near exact duplicates of Ida herself.
Woman: Is this the fat daughter or the one who drinks?
Ida: This is the one with the half-wit factory between her legs.
The episode where Craig is wheelchair-bound and has a helper monkey has the part where the monkey keeps feeding him hot lasagna. Craig asks the monkey to wait for it to cool, but the monkey keeps feeding it to him. He asks for some water, and the monkey puts the straw almost where Craig can reach it before feeding him more lasagna.
Malcolm is about to suffocate in his car and says that Stevie and Reese were right.
Malcolm: I guess that makes it easier. I don't want to live in a world where Reese is right.