Adventure Time: Sandwiches are Serious Business in the Land of OOO. One of the short "graybles" is all about Princess Bubblegum painstakingly crafting the perfect sandwich which Cinnamon Bun just wolfs down without even tasting. In another episode, Jake goes through an elaborate process of evoking the spirit of creativity and stealing a lobster's soul to create a sandwich so tasty that the Magic Man tries to steal it from him.
The Beach Episode from Avatar: The Last Airbender hangs a lampshade on such things with Azula, Ty Lee, Zuko, and Mai playing a friendly game of volleyball at the beach. First, Azula confers with her team and points out that a player on the opposite team has a slightly bad leg, probably weakened by a childhood injury, so they should aim at that leg to defeat her. When Azula spikes the ball and scores the game point, she makes the ball explode and completely loses it:
Azula: Yes! We've defeated you for all time! You will NEVER rise from the ashes of your shame and humiliation!... Well that was fun!
As is dating, (she's only just met the guy and had her first kiss):
The card game in Chaotic is only serious business in parallel universes (two, in fact). On Earth, it is just a very popular game and nothing more.
Only popular enough to play it during lunch at school without people thinking you're a total nerd (which most players are)
On the episode "Earth To Kaz" tends to avert that as well. Anything Chaotic (actually any TCG) is a brand iron used for nerds.
The students of Clone High take everything seriously, including cross-country, film festivals, student council, raisins and litter. Considering that Ponce De Leon meets a grizzly death from a stray plastic bag, they kind of have a point on that last one.
Dexter's Laboratory typically had Dad being the progenitor of Serious Business. In one episode, he goes to insane lengths to get at his wife's fresh-baked muffins as quickly as possible. In another, he insists that Dexter be able to defeat Dee Dee at a snowball fight because Dad used to be a snowball god until he was defeated by...Mom, who explains that she just playfully lobbed a little snow at him one day and he freaked out, at which point Dad realizes he was making a big deal over nothing. In still another, he urges Dexter to join him on a fishing trip.
Dad: Dexter, since the dawn of time man has gone fishing. And not just for our little aquatic friends, but fishing for answers! For understanding! For meaning! So awake, my son, and join your old man in the quest... for KNOWLEDGE!
In the Doug episode "Doug's Dinner Date", when Doug goes to a restaurant and orders liver and onions, a food he hates, everybody at the restaurant, including the staff, reacts with shock.
The basis of Fillmore!! is every aspect of middle-school life is overblown to something everyone's life revolves around. EVERYTHING is Serious Business, including the Bocci Ball team, Standardized Tests, the School Mascot, a Mini-Golf tournament, Macaroni Art, the world's longest-living Tomagotchi Expy, Baseball Card Forgery, Abstract Art, Graffiti, and tricking kids into stealing scooters so he can look good by giving them to poor underprivileged kids in Russia.
Not only are mascots Serious Business, but stealing them is a sufficiently impressive hobby that there is actually a book called Caring for your Stolen Mascot.
In one episode of the Flintstones little-league baseball was Serious Business to the parents, just like in South Park (and real life). After Fred, who was the umpire, made a decision that resulted in the home team's loss, the kids' parents started threatening him up to and including rocks thrown through the windows of his hours. Since Barney was the team coach, it causes a major rift in their friendship.
This was only the parents though, at the end of the episode the kids from the team came to Fred's house and said they thought he made a fair call and accepted it with no hard feelings.
Parodied in Futurama, when the Harlem Globetrotters show up to challenge Earth to a game of basketball. When asked what happens if Earth loses, the Globetrotters reply... "NOTHING! There is nothing at stake, and no threat!" After Earth loses the game, further Lampshade Hanging is done by the commentator, who states that "This is a dark day for humanity. Earth... has been beaten... at basketball." In the DVD Commentary, the creators admit that the entire plot was a jab at the network, who always wanted the stakes to be as high as possible.
That may have something to do with the fact that they take grammar and spelling mistakes very seriously as well. In "The Problem With Popplers", Lrrr seems just as angry at Zap Brannigan for mispronouncing "guacamole" as he is about him eating their young!
Then Star Trek has actually become a religion in Futurama. As explained by Nichols: "As country after country fell under its influence, world leaders became threatened by the movement's power." Since then, all the episodes and movies have been dumped on Omega 3 (a forbidden world) - and it became forbidden to use the words "Star Trek."
Galactik Football to the point that most of the characters care more about the matches than about the conspiracies, kidnappings and political manipulation taking place. To be fair, their version of football involves the Flux, which itself is a perfect example of Mundane Utility.
In King of the Hill's series finale, meat-inspecting is serious business, or at least the competition Bobby enters is. His teammates go batshit insane when he gets one question wrong despite still making it to the finals, then later at a dinner party, one teammate actually throws pepper in an opposing team's faces. And on the way to the finals, the driver of the bus carrying Bobby's team turns out to be a member of the same opposing team, and parks the bus in a puddle of mud and leaves them stranded there.
Hank also treats Propane and Propane accessories as Serious Business. And not in the "It's flammable, so be careful and maintain proper safety when handling it" kind of way. In a "Disrespect or insult it in any way and I'll kick your ass" kind of way.
One episode had Peggy and Bobby deciding they like burgers cooked over charcoal. However, at the end Peggy pretends to prefer burgers cooked with propane in order to keep the peace.
Everything is Serious Business in Arlen. Going against the majority on anything that doesn't make sense is almost certain to get you branded a pariah, dragged to court or jail, or most likely all of the above.
The Daffy Duck featured in The Looney Tunes Show takes everything way too seriously like he thinks that getting his newspaper is more important than anything (he doesn't read it he uses them to make a float of himself) and thinks that if it doesn't arrive one day that means someone stole it, and he nearly ends his friendship with Porky Pig because he took some fries from his basket, the fries were for everyone.
Dethklok are so popular, their fans will go to their concerts despite the ridiculously high risk of dying, some will kill themselves if an album is delayed, a secret agency exists whose sole goal is to kill Dethklok, they have thousands and thousands of workers constantly putting their lives in danger just to serve every single one of Dethklok's (often ridiculously stupid) desires, Florida's governor was killed by rabid fans just for a negative comment about Nathan, people who download their music are tortured (often by Dethklok themselves), and the band themselves are the world's twelfth largest economy. In Metalocalypse, everything Dethklok related is very Serious Business.
It's subverted as well, because the band members themselves do not take anything seriously and frequently display outward hatred towards everyone who worships them. They are, in fact, in it only for the music, the money, and the sheer decadence that comes from the first two.
In fact, Dethklok IS a nation, with the world's 12th highest GDP. And it's just 5 guys and the people that work for them.
Dethklok is also a god, their songs have the power to form whirlwinds and summon ancient beings.
°Mucha Lucha!. Lucha Libre has saved the world several times, and the characters center their lives around it. Even the opening theme's lyrics say Mucha Lucha, Mucha Lucha! It's a way of life!. On occasion, the characters refer to "HONOUR! TRADITION! FAMILY!AND DONUTS!" as the motivation behind their actions (yes, the donuts are Serious Business too).
In "Green Isn't Your Color", we see that secret-keeping is Serious Business to PinkiePie - so much so that she will issue Implied Death Threats and break the laws of physics in order to enforce it. "The Last Roundup" serves as a stark reminder that, if you value your continued existence, you never ever EVER break a Pinkie Promise.
"Winter Wrap Up" is Serious Business to the denizens of Ponyville, as noted by Twilight Sparkle. In fact, the whole show treats the whole "custodians of nature" thing the ponies have going on incredibly seriously. The forest just outside of town seriously freaks the ponies out because hibernation, seasons, weather, and nature in general get on with things, completely devoid of pony assistance. Also it's home to a number of dangerously mythological creatures, but that's just, you know, wildlife. Justified in-universe: It's implied that the whole world is like this, so if the ponies don't take care of things, everything will stay the same. Unchanging. Forever.
Twilight Sparkle herself has a few examples of her own:
Studying. Before you say "but studying is important in Real Life too," consider that Twilight honestly believed she would be sent all the way back to Magic Kindergartenfor just ONE late homework assignment. This proves severe enough that she decides to make a problem if she can't find one, which ends up in her accidentally brainwashing the whole town, requiring the intervention of the Physical Goddess who also happens to be her teacher - all of which nearly gets her in trouble for real. In fact, her final mental plunge is triggered by a scene wherein she expresses her fears to her friends, who promptly dismiss these worries as mere paranoia.
In this same vein, she spends her first-ever slumber party consulting a book about throwing slumber parties, which she is so insistent on following to the letter that she is unable to help remove a tree that's crashed through her bedroom window because she's desperately searching the book for advice on how to respond. Justified since not only is this the first slumber party of Twilight's life, but she's gone most of her life without any appreciable level of social interaction in general (thanks to her aforementioned obsession with studying). Moreover, it's probably safe to assume that Twilight Sparkle has a book about EVERYTHING, and that mostly everything to her is Serious Business.
Universal comprehension. After being faced with a series of phenomena that confounds her logic (courtesy of Pinkie Pie, of course), she devotes the entire length of "Feeling Pinkie Keen" to her investigation - even after repeated instances of serious bodily harm - before finally conceding that there are some things that defy an easy explanation, and that's okay.
"It's About Time" has Twilight becoming increasingly panicked and unhinged (not to mention injured) in her attempts to prevent an unknown disaster she was warned of by her time-travelling future self. The other characters put themselves under no such stress worrying about something they can't prevent, and at the end it's revealed that the very reason Future Twilight went back in time was to warn her past self not to worry about FutureTwilight'swarning.
Cutie marks work recursively since they are an indication of what the bearer considers serious business, be it apple-farming, fashion, or even popping balloons.
The only ones who really consider cutie marks themselves to be Serious Business are the Cutie Mark Crusaders. True, everyone looks farward to getting their cutie mark, but the Crusaders are the only ones who actively seek them and freak out about not already having them. But given the way they're treated by Diamond Tiara and Silver Spoon for not having theirs, itís hard to blame them.
In "The Super Speedy Cider Squeezy 6000", apple cider is this for Rainbow Dash. Hell, her frustration with Pinkie Pie, who beats her in line every year for its sale, is such that she looks forward to rubbing her acquisition of the cider in her friend's face almost as much as she looks forward to actually drinking it. And in the episode "Bats!", Rainbow Dash is convinced that they need to get rid of the vampire fruit bats because the infestation could cause cider season to be cancelled.
In the episode "Pinkie Pride", party planning is this to Pinkie Pie. She felt that Cheese Sandwich was going to replace her as Ponyville's Party Planner, so she challenged him to a "Goofoff."
The Penguins of Madagascar episode "Mr. Tux" turned Miniature Golf into this when an armadillo (The Amarillo Kid) showed up demanding Private give him the satisfaction of one last game of mini golf with Mr. Tux (Private's alterego in a former life). Even Mort remarks on the "high stakes" of the situation when the Amarillo Kid threatens to blow up the zoo if Private loses.
In "Does This Duckbill Make Me Looke Fat?", Perry (in Candace's body, but that's another story) stops Doofenshmirtz from stealing every fast food restaurant clown figure in Danville. Even though we are talking about a massive theft of property here, it still seems rather silly that both Major Monogram and the local police give this matter top priority.
Speaking of Candace, the whole "busting my brothers" dream is practically her way of life.
It's Doofenschmirtz's whole schtick. Often it's lampshaded that he could solve whatever's bugging him quite simply (e.g. moving a chair to another window), but usually dismisses it as "too much hassle" and instead builds is Inators to change everything else (e.g. moving a building blocking his view).
Would you believe noodles? In the European/Korean animated series Pucca, the noodles made at the local Chinese restaurant are such Serious Business that in one episode, when the chefs believe themselves disgraced because of a just-barely-unfinished bowl of noodles, they go to a DEATH COURSE to redeem themselves, while in another, when they split up into three separate restaurants over a fight, it causes a sort of Zombie Apocalypse, with most of the inhabitants of the village wandering as an aimless, lifeless, pathetic mob, mumbling and moaning about the lack of noodles until they reunite.
And God help you if you run out of chopsticks. The world will scream.
For most of Ratatouille, this is averted, with food only being given relatively reasonable import (it is a movie about chefs, after all, so a little of this is to be expected)... until the climax, when Remy's cooking — and the revelation of his role as the chef — are enough to induce a Heel-Face Turn in a sadistic critic.
On paper the games in ReBoot sound like it is serious business, but it is justified because these games are a life-or-death matter for the people inside the computer.
Everyone slowly becomes addicted to a jigsaw/card game thing called "Ajimbo", becoming like zombies that forget how to play other games like kickball. Subverted (kinda) with the implication the puzzle is an addictive Artifact of Doom.
In one episode, collecting and trading "Monstickers" escalates to the point where it became the playground's currency. Everything has a fee, even such activities as laying on the grass. It gets even worse when T.J., driven to become the richest kid on the playground, monopolizes every activity, and starts charging kids stickers for standing around because they can't afford to play anything (he calls it a "loitering fee").
There's also the episode where they find the book of King Morty's rules. In the world of Recess, playground monarchs are serious business. Taken a step further with King Morty's rules. He was the first king, so his words are akin to gospel.
In the episode where the word "Whomp" is branded a swear word, SWAT helicopters come in when the word goes out of control.
In Regular Show, anything and everything can be serious business, Rock paper scissors summoning an Eldritch Abomination, Death's preferred method of gambling for souls being arm wrestling, posting viral videos being grounds for an And I Must Scream. Most of the plots start with something harmless before snowballing into a Cosmic Horror Story.
In an episode of The Simpsons, barbershop quartet music is Serious Business: Homer and the Be-Sharps start touring around the world, and as Homer's agent put it, "women are going to want to have sex with you". Granted, it was a spoof of Beatlemania, but still.
What really takes the cake is "Cartoon Wars". Many characters treat Family Guy having an episode with Muhammed in it like the start of World War Three, and Kyle nearly dies trying to stop Cartman from getting it canned.
"Douche And Turd" takes it Up to Eleven, when Stan's refusal to vote got him threatened, banished and nearly killed.
At the end of "Quest For Ratings" when Craig's show falls in the ratings the AV teacher orders him to be suspended from school and puts in a request for the surgical removal of his testicles, just to reinforce how important ratings are.
Spongebob, himself, is a walking example of this trope, actually. He cries and freaks out over things that aren't that serious. He once cried about arriving to the Krusty Krab one minute late. Even Mr. Krabs lampshades this and says that Spongebob arriving one minute late wasn't that serious.
In Thomas the Tank Engine, everything on the Island of Sodor is somehow connected to the railway to such an extent that every delivery made on Sodor is delivered by rail.
Similarly, racing is something nearly all the locomotives take seriously.
The bad guys in Totally Spies! take completely mundane things seriously as part of their evil scheme/revenge. An evil toy maker brainwashes adults to be kids again, because they stopped playing with his toys. Or an evil fashion designer mutating people into animals and use their fur to make her design clothes.