Pick a trailer, any trailer, for any episode of a 2010s Cartoon Network series. You've basically seen the entire episode in under 30 seconds.
For a particularly egregious one, the beginning of the trailer for Teen Titans Go!'s "Justice League's Next Top Talent Idol Star" (no, that's not a typo) shows that Robin, Raven, and Cyborg were the final contestants.
In the few days after Stevenbomb 4 alone, 2 clips were released on Cartoon Network's UK site as promos that revealed the return of Malachite and Lapis Lazuli, with said episode not airing until four months later.
It's arguably worse with the "Steven's Summer Adventures" event, during which the network aired the entire third season within a month and released significant portions of almost every episode early as "sneak peeks". In a particularly irritating move, they also uploaded clips and made news articles surrounding Bismuth being introduced, in which it is also shown that Amethyst has received another design change. It kind of makes you wonder whether any major development in the show will ever be allowed to go un-spoiled ever again.
Possibly the most notorious case was in May 2018, due to it being an accident rather than an intentional marketing choice by the network. As part of a miniseries about animation production called "Drawn Podcast", Cartoon Network released an interview with Rebecca Sugar and Ian J.Q. In the video were short clips of unreleased episodes that were regarded as major spoilers for the remainder of the season, the most damning one being the final clip, which showed Steven peacefully interacting with Blue and Yellow Diamond before being set down next to the Crystal Gems, which includes a un-bubbled Bismuth: something that greatly changes the show's status quo. Even worse, this came after many members of the Crewniverse begged the fandom not to spoil upcoming episodes. Needless to say, fans were furious at the network and members of the Crewniversewere pretty distraughtnote Ian's original tweet is now deleted. The video was quickly pulled by the network upon realization and reuploaded without the spoilery parts, but by then the damage was done. Most of the spoiled episodes would air two months later, with the episode featuring that final clip premiering online the following month.
A less spoilery example, but one promo for the Regular Show episode "Go Viral" actually showed the ending of the episode (more specifically, the Farting Bear that was a Running Gag in it landing on Muscle Man).
The Russian version of Cartoon Network proved to be extremely spoiler filled twice. First, it revealed Unikitty! before Cartoon Network announced the show, and then revealed what Bliss looked like prior to the Power of Four PPG 2016 special.
The Season 2 preview spoils a few scenes, such as Anne fighting Sasha again, Anne and the Plantars finding Anne's other friend Marcy, and as far as the posters show, Anne holding the Calamity Box, hinting she retrieves it sometime when the season begins.
The Season 3 preview wasn't much better, as it showed Marcy being possessed by King Andrias' master, which doesn't happen until the end of the episode where General Yunan and Lady Olivia try to rescue her.
Played with in Archer. The first episode of Season 5 ends with a Fantasy Sequence of Archer's that serves as a trailer for the rest of the season. It did include some genuine spoilers, but they were interlaced with things that never happened (like Cherlene getting kidnapped) and things that happened in completely different circumstances (like Lana going into labor).
When Batman: The Animated Series originally aired on Fox, some of its promos could be pretty spoilerific, too. This one outright shows the cliffhanger ending of "Heart of Steel, Part 1" in it.
The promos for "Green Christmas" completely spoil the final scene of the episode, such as the Greens spending Christmas Day and the final song number, right down to the very last shot.
The promo for "Chipocalypse Now" spoiled the scene where Cricket jumps off the Megastore roof to escape death in the hands of Chip.
Promos for the first two Bionicle: The Journey to One episodes spoiled most of the ending by showing the sought-after Mask of Creation in the hands of the villains, from the very last scene. The only things not to get spoiled were Umarak kidnapping Ketar and mutating into a hulking beast upon putting on the mask, but these were already Spoiled by the Merchandise aynway.
One commercial for the series finale of Danny Phantom, "Phantom Planet", had the announcer outright state that Danny would loses his powers, get his powers back, have a Last-Minute Hookup with Sam, and team up with every ghost in the series to stop the Disasteroid.
Dora the Explorer LOVES doing this, especially spoiling Dora's final outfit or transformation that she receives in the climax. Even the merchandise spoils such.
During its original airing on The Disney Afternoon, the trailer for Part 1 of the DuckTales (1987)Grand Finale, "The Golden Goose", showed the cliffhanger ending of Huey, Dewey, and Louie getting turned into gold statues.
More Disney Channel screwing: In a Fish Hooks episode "Fail Fish", Milo has to pass a test in order to prevent himself from being held back a grade. This would have been taken as a surprise, if only they hadn't shown him holding the test in his hand while he shouts for joy, implying that he has passed it! You might not be able to catch it if you're not paying attention, but it's still there.
This print advertisement for The Flintstones special "Hollyrock-A-Bye-Baby" shows that Pebbles will have twins.
The official trailer for Hamster & Gretel shows that Hamster can talk, which isn't revealed until literally the last few seconds of the 1st episode, as a closing joke.
Black Phantom's defeat from the Hero Factory TV special was spoiled, shot for shot, on an on-line promo vid advertising the cartoon and characters (and their toys) on the LEGO website.
Nickelodeon showed various commercials of scenes leading up to the release of The Movie of Hey Arnold!. One of these completely spoiled that Helga finally confesses her love for Arnold. (They didn't show how he reacted to it, though.)
One Netflix preview clip for Season 2 of Human Resources (2022) consists of the final scene (and musical number) of the series, which also spoils that Rochelle turns back into a Lovebug for anyone who started but didn't finish Season 2. Even worse, these clips play automatically when you click the show details on Netflix.
Invincible (2021) averts this trope in the announcement for the release date of its second season. The trailer has Invincible and Allen in a restaurant, discuss about the latter's findings about the planet Urath, but Allen has failed to find the planet. Allen then asks Invincible on when more content of the Invincible TV series will arrive for the world to see. Invincible responds to Allen that the TV series will come soon, but Allen refuses to take a vague answer. Invincible quickly thinks up of a release date for the TV series to satisfy Allen, which is to announce that the TV series will arrive in late 2023. Invincible's response satisfies Allen with the revelation that a release date has been announced, but is unsure of how long it will take.
As if that wasn't enough, one of said ads actually showed a clip of Kim being shocked by Eric while he had an evil look on his face, which would pretty much give away that he's really working for Drakken.
The trailer for the first season finale for The Legend of Korra was shown when there was still one episode to go before it, and spoiled that the Equalists will get control of the city and begin mass bending removal.
Several promos for "The Rise of Scar" show Scar being risen and Kion using the Roar in anger, which is indeed what happens near the end. Even the description spoils it. It's even right there in the title.
The synopsis for "Battle for the Pride Lands" says Kion and Ono are injured in the battle against Scar and his army, which is indeed what happens to them near the end. It even spoils the very end where they leave in search of the Tree of Life, which explainstheir whereabouts in Simba's Pride.
The YESvember music video on Nickelodeon's YouTube channel includes a scene from the episode 11 Louds a Leapin', spoiling the reveal of Mr. and Mrs. Loud's faces. The video was eventually reposted with that particular clip replaced with a scene from The Thundermans episode "Winter Thunderland".
The Brazilian channel Gloob has become fairly notorious among Miraculous Ladybug fans for releasing episode trailers that contain massive spoilers for the episodes in question
A promo for the Motorcity episode "Like Father, Like Daughter" spoiled the ending in which Julie agrees to take over KaneCo should something happen to her father.
A promo for the Mickey Mouse Clubhouse episode "Dr. Daisy M.D." spoiled Mickey and Daisy working on Pete, who is the "mystery patient" for the episode.
The trailers for the episode "Magical Mystery Cure" included a clip of Fluttershy saying "You look just like a princess!", completely spoiling the game-changing twist (That everyone already knew about) that occurs the very end of the episode. And then, Hasbro proceeded to plaster this plot twist all over all over their commercials and toys. Additionally, a sign depicting Twilight Sparkle with wings was actually sighted months before the episode was even announced, but was dismissed by most as an error from the artists while creators of the show even tried to save the twist by outright lying about it.
To the great annoyance of viewers who had spent most of season 4 (if not longer) awaiting the frequently-referenced Equestria Games (and especially of Rainbow Dash fans), a promo for the final episodes of the season included a very brief clip of Spitfire crossing the relay finish line narrowly but noticeably ahead of Dash.
Also, a promo for the Season 4 finale "Twilight's Kingdom" shows that the Golden Oaks Library, where Twilight has stayed since moving to Ponyville is destroyed by the new villain.
In the Hub trailers for the finale as well, the Royal Sisters and Princess Cadence lose their Cutie Marks when they transfer their magic to Princess Twilight, leaving them helpless to being made hostages/prisoners of the new villain. [1][2][3][4] The trailer also shows Twilight taking off so fast, she leave a crater in the ground, against a blood red sky. About the only thing the trailer for the finale didn't spoil was that said villain was a FIM version of classic villain Tirek.
The Discovery Family promo for season 8 features a particularly bad example of this, spoiling lots of big surprises like Starlight and Sunburst getting called by the Cutie Map, the return of Queen Chrysalis, and Spike getting wings. Meanwhile, the synopsis for the season finale indicates Cozy Glow intends to take over the School of Friendship. This is despite the fact said character wasn't even introduced yet, and when she was, she was a simple one-shot character about halfway through the season.
In My Little Pony: Equestria Girls – Magical Movie Night: Movie Magic, the plot involves figuring out who is sabotaging the production of a movie. The synopsis for Mirror Magic indicates that Juniper Montage seeks revenge. Do the math.
"Get Off My Lawnie"'s official summary only describes the very end of the episode (Granny Tentacles getting her own show), and not the lead-up of her being pestered by unwanted fans; the fact that she actually gives in and decides to do it is the twist.
The promo for "Now Museum, Now You Don't" showed Patrick recreating The Birth of Venus, which happens at the end of the episode after Lady Upturn makes him and Cecil replace the art they broke.
Promos for "10 & 1 Toilets" showed the ending where GrandPat is standing naked on a runway after being attacked by Tinkle and his puppies.
A promo for "Family Plotz" included the ending scene of Cecil serving soup to the zombies.
Promos for a premiere week also included the ending gag of "There Goes the Neighborhood" where Cecil shows up in Patrick's ice cream cone.
A promo for "Movie Stars" included the scene of SpongeBob and Patrick changing into their superhero outfits, which doesn't happen until near the end.
Every single trailer for "Summer Belongs To You" spoils the ending where the gang arrives back home and celebrates with a concert. There's also a scene of them jumping a gorge without their Sun Beater 9000.
The commercials for "Minor Monogram" literally only showed the ending where Vanessa falls for Monty.
The commercial for show's Grand Finale "The Last Day of Summer" completely spoils the end finale number "Curtain Call (Time Spent Together)".
The commercial for the week of new episodes in August 2016 spoiled Face 9000's new look.
Sometimes, this is a case of Episode Descriptions Always Spoil. For example, the description for "Mindy's Meteorite Stand" spoils the fact that Mindy's meteorite really wasn't a meteorite, but the big rock she was sitting on is, "Sunday Drive"'s description spoils that the Propulsions weren't on Mars, but an Earth desert, and the description for "Mindy's Mystery" spoiled that the mystery smell came from moonflowers, and the bright light that was bothering Mitchell was from the moon itself.
Zigzagged for the images the wiki provided for Season Two. While some images are tied to the episode's theme, some are just random screenshots. A few ridiculous examples of the latter include: The image for "Zerk Visits Earth" doesn't feature Zerk, the image for "Sunspot's Sunspot" doesn't feature Sunspot, the image for "Sean Has a Cold" depicts Sean as completely healthy, and the image for "Mars Rock For Mom" is a frame from the the takeoff sequence.
The theatrical trailer for Rugrats in Paris had Don LaFontaine proudly introduce Kimi as "the newest Rugrat", therefore cluing the viewers in on how the movie ends (Chuckie's dad marries her mom) and her incorporation into the show.
Parodied in The Simpsons with an old Radioactive Man film reel. A giant missile heads toward Earth, and cuts to a freeze frame while the announcer says, "Will Radioactive Man save the planet Earth? Find out next time!" The freeze frame shows Earth being split in half with a giant mushroom cloud.
That's more a parody of old adventure serials. They routinely ended with something terrible happening (e.g., the hero's car skids off a cliff) and an admonishment to see the next installment to find out how the hero would avoid his terrible fate. Invariably, the next installment would be a total cheat (e.g., the hero jumps out of the car before it reaches the edge - even though he was clearly in the driver's seat as the car went over in the previous installment).
The promos for the episode "How Munched is That Birdie in the Window" spoiled the whole plot of Bart adopting a wounded pigeon and Santa's Little Helper eating it.
The trailers for The Simpsons Movie show the exchange among Homer, Bart, and Russ Cargill near the end of the movie with the "treasure of I'm a weiner" joke. This spoiled the "To Be Continued... Right Now" joke as the latter takes place before the former in the movie, showing there is more.
The syndication promo for "When Flanders Failed" had Bart facing the bullies with his "karate skills". The announcer asked, "Will Bart get a black belt or a black eye?", followed by a cut to Bart hanging from a basketball hoop by his underwear.
Promo pictures for "Lisa the Boy Scout" included the scene of Frink on Mars, the two hackers, and the flashback to Bart's future self in the series' first episode, hinting beforehand that the episode would be much stranger than the straightforward title and summary suggested.
Parodied in the South Park episode "Professor Chaos":
Though that may have been intended as a parody for the (in)famous "Who is Eric Cartman's real father?" 2-parter, since a lot of fans were ticked off when they got the Terrance & Phillip special after waiting for a month, instead of the continuing story.
The made-for-TV movie "Atlantis SquarePantis" spoiled the climax where Plankton finds out he stole a tank that shoots ice cream. It wasn't like it was in a montage or anything either, they blatantly displayed it up front because they thought the punchline was funny enough to include. It got even worse when they put a Commercial Break Cliffhanger right before this moment.
The episode "Squid Noir" was completely spoiled, when Nickelodeon launched a block called "You Bring The Color", and the website called youbringthecolor.com to use the pictures from the end of this episode so kids can color the characters from the ending. No one even knew, until the altered ending got aired.
The ending song from "A Place for Pets" was posted on Nickelodeon's social media before the episode premiered.
Similarly, the twist ending featuring the return of Handsome Squidward from "The Two Faces of Squidward" in "Squidward's Sick Daze" had been officially posted on social media before the episode premiered.
A clip from the ending of "Potato Puff", of SpongeBob crying after the potato is mashed, was uploaded to Nickelodeon's GIPHY before the episode came out.
"Upturn Girls" was also spoiled by GIPHY, with a clip of Pearl and Narlene on top of Upturn's as the security guards close in on them, then them escaping using bubble gum.
The ending of "Ain't That the Tooth", with SpongeBob and Patrick seeing the tooth fairy and being made her assistants, was shown in promos.
A scene near the ending of "The Flower Plot", where Squidward proposes to Petunia and she explodes, revealing her to be Plankton, was posted outright on the SpongeBob Instagram account four days before the episode came out.
The ending of "We Heart Hoops", with SpongeBob and Patrick being held in hoops by Old Man Walker and Patrick saying "classic," was shown in the promos.
The series restrained itself fairly well when it comes to foreshadowing Anakin's eventual transformation into Darth Vader, so naturally Cartoon Network was eager to promote an episode where Anakin has a vision of what he will become. Some pretty sweet clips were shown in the promos, but when the actual episode was aired, you realized they showed you the whole scene!
"Deal No Deal"'s original released synopsis is "Trace makes a rash decision when she learns what they are transporting is for the Pyke Syndicate." The problem is that this rash decision is a late-episode plot twist that comes with less than six minutes left to go.
The season 2 midseason trailer showed somewhat more of the finale than Dave Filoni would have liked, in particular the Sith holocron, the return of Darth Maul and Ahsoka and Vader's duel. However, it did not spoil some particularly major plot points, namely Ahsoka's Uncertain Doom and Kanan getting blinded.
It's not a surprise to anyone keeping up with the show, but the season 4 trailer has a shot of Kallus in a Rebel uniform, which to anyone only familiar with his character from the first two seasons would be unexpected to say the least.
Star Wars Resistance: The first season 2 trailer revealed that Kaz's father Senator Xiono, believed in the season 1 finale to have died in the destruction of Hosnian Prime, is alive.
When The Transformers episode "Dark Awakening" was rerun prior to the third season finale, Rodimus Prime's final line, "So long, Prime," was replaced with an announcer declaring, "But is this really the end of Optimus Prime? Tune in for tomorrow's exciting episode: 'The Return of Optimus Prime'!" Infamously, the original DVD release of this episode back in 2003 (specifically, Rhino Entertainment's The Transformers Season 3 Part 1 DVD) featured this alternate ending. Thankfully, newer DVD releases go with the original ending (though of course the DVD's episode list does let you know that an episode called "The Return of Optimus Prime" is coming up.)
This trailer for VeggieTales: God Wants Me to Forgive Them?!?!, shows Junior doing exactly that at the end.
And the trailer following it for Dave and the Giant Pickle also spoils that the titular pickle is defeated at the end.
Along with the trailer for Josh and the Big Wall stating that "the walls will come tumbling down".
A promo for Wow! Wow! Wubbzy!'s week-long second-season premiere event that airs one episode a day, also known as Wub Week, focused on Daizy, who was just introduced. One of the clips showed Daizy kicking a kickity-kick ball from the episode "Who's That Girl?", spoiling the ending of said episode.
Promos for the second season premiere of X-Men: The Animated Series blatantly spoiled that Morph was back from the dead and now evil.
A press release dated a month before the first episode of Stan Lee's Superhero Kindergarten aired spoiled the existence of Emerson, a character who appears in the first season finale.
were pretty distraught