The lush, detailed opening credits contain information about the cast or plot that nullifies surprises later in the series. Thus, it's pretty obvious that when someone apparently important shows up who isn't in the opening credits, they aren't going to be around for very long. Similarly, the series tries to pretend that someone isn't very important, but they're featured prominently in the credits.
Series that rely on Previously On in order to keep viewers up to speed are especially prone to this. Because only the parts of the story arc relevant to the current episode get recapped, the viewer is tipped off that those parts of the story arc are about to show up.
This is also particularly common in adaptations, because the producers often assume that many viewers will already be familiar with at least the basic outline plot, because many viewers are only there because they want to see spoilery stuff from far ahead in the plot, and because adaptations of Long Runners naturally have more they can spoil. In cases like those, it can also qualify as a Late-Arrival Spoiler.
A series can get around this by shaping their opening credits to merely be foreshadowing, a new or edited differently opening at various points in the series, or have the opening have little to do with the actual plot.
A variation is where vaguely famous names appear in the credits, so you can guess automatically that they're going to be fairly prominent in the episode before they even show up. In series with recurring characters that are not normally in the credits or a cameo from someone who left the show this can indicate their eventual presence in an episode ruining their unexpected entrance.
An overlap with Foregone Conclusion at times happens. Contrast with Bait-and-Switch Credits. If you're spoiled for the first season when you look up the opening for the second, that's a Late-Arrival Spoiler. May be averted with Evolving Credits, where credits change with the story instead of revealing everything at once. Dead Star Walking can be either a subtrope of this or an aversion, depending on how it's presented. Contrast Not Named in Opening Credits when an actor's name is omitted from the opening credits to maintain a surprise. See also First Episode Spoiler, which can often fall prey to this. As a Word of God once explained, the American Screen Actors Guild has strict rules about where credits can appear, at least partially justifying this trope.
Since this is a spoiler trope, there will be unmarked spoilers below.
Averted in Sleuth, which deliberately features an opening cast list which proves to be wildly inaccurate.
Saving Private Ryan's opening also serves, but is kinda ambiguous to those without knowledge of the American Army: the old man is wearing a pin of the 101st Airborne (Screaming Eagles), and Ryan was the only principal character in the film in that division.
Disney's Robin Hood did this by showing detached scenes from the movie's plot points in the opening credits. Every relevant character in the movie is shown with an animation of them solo from various important parts of the movie, and the animations for the rest of the credits is from the climax.
The MockbusterParanormal Entity takes this to extremes. Three minutes into the film, it is revealed that the protagonist's sister is dead, he went to jail for her murder, he hung himself, and then his mother (who got possessed) hung herself too. The remaining 87 minutes of the film are pointless.
The opening credits of GoldenEye make it fairly plain that we haven't seen the last of Sean Bean, despite his character being "killed" before the credits even rolled.
Want to watch Bedknobs and Broomsticks and not know the ending? Stop watching the opening credits when Donald McKayle is credited for the choreography!
In the film adaptation of Eragon, along with being almost nothing like the book, the audience is informed of the fact that Arya is a princess during the opening narration and plot set up. A fact that readers didn't find out about until halfway through the second book.
Tangled: Flynn Rider announces he will die as the first line in the movie. He gets better.
Subverted in Rango. The owls say he'll die, implicitly at some point during the storyline. At the end, when it hasn't happened, one owl suggests he might die from a household accident. At some point after the timeframe of the movie.
In the film Horsemen (starring Dennis Quaid), Ziyi Zhang has second billing in the opening credits. Even if you didn't recognize the name, the fact that she's the only Asian actor in the movie gives away the fact that her character is more than she seems to be when she is first introduced.
The opening narration of Moulin Rouge! by Christian clearly states "the woman I loved is dead."
The opening narration of Hop spoils the fact that the main human character becomes the first human easter bunny. This concept isn't introduced untill a little before the climax, after a movie of basically nothing happening.
The German version of The Who's Tommy has an opening narration that states "Tommy can not be dubbed!" in this exact words. The narrator then proceeds to give an overview of the films plot which means he gives away every plot twist until the very last moment of the film as if he was reading the synopsis off of Wikipedia. The narration also plays over the first two minutes of the film where Tommy's parents meet until the start of the war and cancels out any music. Then the movie proceeds with subtitles, making the inclusion of the narrator completely pointless.
The opening several minutes of Melancholia play out the entire plot in a series of stylized images.
I've finished my war book now... It begins like this:
Billy Pilgrim has come unstuck in time.
It ends like this:
The cover of the third book of The Icewind Dale Trilogy shows the heroes fighting demons in Tartarus, which only happens at the very end of the book. Also, Bruenor is shown on the cover, who was thought dead in the previous book and makes a surprising return in this book.
Stephenie Meyer managed to spoil Twilight's plot twist on the back of the book. Then again, Edward being a vampire is the entire premise, so it's not like anyone picked the book up without already knowing the twist.
The first page of The Last Guardian says (at the bottom, in Gnommish): The Last Will and Testament of Artemis Fowl.
If you're reading one of Edward Rutherford's multi-generation historical novels (Sarum, London, etc), don't even glance at the family tree at the front of the book until you've read the whole thing: it'll spoil who has kids with whom, etc.
Live Action TV
Extremely common in American TV series produced in the 1970s and early 1980s, particularly crime and action-adventure series. Pre-credit sequences frequently consisted of montages of scenes from the episode, sometimes including surprisingly major spoilers.
Mission: Impossible. The old tv series' opening credits has a montage of basically every major plot point for the episode. Of course, the viewer has no idea what any of it means at that point.
The films also do this (though only in the fourth the succession isn't fast enough for viewers to discern the images).
The Wire had some AMAZING opening credits sequences (due mostly in part to the various renditions of "Way Down in the Hole" over some really jarring montages) that occasionally would drop scenes that you're looking for the entire season (if you watched it all on DVD). While you can't tell it's Stringer's hand unzipping D'Angelo's baby mama in the credits it did seem a little weird when it finally happened.
Community has a spoiler ending in the penultimate episode of the second season, when the Dean of a rival school is listed in the credits. He is disguised as an ice cream mascot and masterminding the entire situation.
Buffy was very egregious with this. Angel's actor would be listed in the first episode of season three, while ostensibly being sent to a hell dimension at the end of two. Actors whose appearance on the show should be a twist (Oz when he had left, Buffy's mom after she died, and so on) would almost always be mentioned up front.
The opening credits of the Buffy pilot didn't include Xander's friend Jesse, so it pretty obvious that he wasn't going to survive, Joss had wanted to include him but they couldn't afford to make two different opening titles so this was nixed but he always claimed he wanted to do it. As a consequence, when Tara was added to the credits for her last episode on the show, that made her departure an easy guess for those who knew about the Jesse thing.
Angel averts this with its season two finale, which guest stars Alison Hannigan as Willow, who shows up at the Angel Investigations office to inform Angel that Buffy has died. The same trick from Buffy's "Two to Go" episode is used to hide the actor's identity. Which makes sense since in both cases, the actor in question shows up at the very end and only has a single line of dialog.
The 3rd season opening of Buffy shows Faith before she even makes her first appearance. Averted in season 1, it doesn't hint that Angel is a vampire.
In the first episode of Firefly aired, the crew (consisting of everyone in the credits) has already been assembled. However, the unaired pilot shows how three of the crew came to join. On the DVD order, the pilot comes first, but uses the credits created for the season as aired. This renders a huge plot point of the episode - finding out which of three passengers is an enemy spy - completely redundant, as two of them are listed in the opening credits. The credits also clearly show River In A Box, which is intended to be a major twist.
Criminal Minds did this big time in Season 7. During the previous season, Paget Brewster's character was written off by apparently killing her and eventually revealing that she was in Europe under witness protection, heavily implying that her character was never coming back. Well, guess whose name and face were prominently featured in the opening of the first episode in Season 7?
Star Trek: Voyager did this in the fourth season, with its second episode being advertised as one where "a crew member leaves forever, and you'll never guess which one." Except that the opening credits for the first episode no longer showed "Jennifer Lien as Kes," replacing it with "Jeri Ryan as Seven Of Nine."
Voyager also did this in the second season premiere, involving an episode where the dramatic tension and "big reveal" of the episode revolved around the crew of the eponymous ship discovering Amelia Earhart and other humans abducted from the 1930s on an alien planet. Too bad the big reveal was really revealed in the opening credits by listing the critical "surprise" role.
The Season 8 opening to Mystery Science Theater 3000 spoiled the return of Pearl Forrester (at the end of the first episode) and the "chase across the galaxy" storyline (several episodes in). This is probably because season 8 was really the only season to have a plot, at the insistence of Sci-Fi Channel execs. It should also be noted that, when the episode originally aired, it didn't have that opening. It showed Mike and certain Bots returning from the edge of the universe and that was it.
It should also be noted that anybody who feels upset that the plot of Mystery Science Theater 3000 has been spoiled is probably missing the point.
The third season showed Starfuries fighting Starfuries, which signified a major change in alliances (and wouldn't happen until half way through the season).
Another B5 example, this an aversion that didn't stay averted: at the end of the second episode of season 2, a character who hadn't been seen yet that season was revealed to have a whole new look. In the original run, the first two episodes' credit sequences showed her as she had looked previously, and all later episodes showed her as she now looked. Unfortunately, in subsequent runs and the DVDs, the later credit sequence was used for the first two episodes, blowing the surprise completely.
Yet another spoiling intro is in the fourth season: G'Kar saying that it was the year "we took back what was ours." Maybe it's tradition.
Also, when Anna Sheridan turned out to be Not Quite Dead, the guest star credits at the beginning listed "Melissa Gilbert as Anna". Leaving off the surname might have worked, as Anna Sheridan had previously been played by a different actress, if Gilbert weren't Bruce Boxleitner's real-life wife.
A more obvious example of this trope is the guest star credit "Julie Caitlin Brown as Na'Toth", when she turned out to be Not Quite Dead as well. Unfortunately, they couldn't pull the same trick again as Na'Toth had Only One Name.
The 2000s Battlestar Galactica has a "previously on" bit before each show, which allows you to infer exactly what situations will be present during the episode due to what they choose to show you during the opening scrawl. The scenes shown could be from many, many episodes ago, relating to events that have not been referenced since, making it obvious that the story arc would be continued in the following episode.
Each episode's title sequence ends with a montage of scenes from the current episode, wilfully courting this trope. Word of God is that the montages were introduced in homage to Space1999, which did the same.
BSG has a weird habit of showing clips in the 'Previously on' that never actually happened, either things that were edited out of previous episodes or scenes featuring guest stars where this was their first episode.
Except not really once the miniseries and webisodes are taken into account. Anyone who started with Season 1 would be very confused about half the interactions, unless they had seen the miniseries-that-really-isn't-anymore
BSG specifically avoids this in the Season 3 finale "Crossroads, Part II" - Katee Sackhoff does not appear in the opening credits, but is credited at the end of the episode, after Starbuck returns from the dead.
They do the same thing in the season 4.5 premiere with Kate Vernon as Ellen Tigh.
The series carefully avoided this several times. The first episode opening is slightly modified, so as to avoid showing you the wormhole (which won't be introduced until half way through the episode). The first episode of the third season actually uses the second season opening, since the third season opening contains the Defiant, which is introduced in that episode.
In the episode "Heart of Stone", the Female Changeling posed as Major Kira in an attempt to persuade Odo back to the Great Link. In order not to spoil the ending, the actress agreed to be listed in the ending credits, instead of the opening guest star credits.
Nicely averted by the episode "Duet", in which the actor playing Marritza is listed, as Marritza, immediately after Odo identifies him by name. Actually a Double Subversion: for most of the episode, we are led to believe that the character's real identity is Gul Darhe'el, and if this were true, the credits would be deliberately misleading; however, it's revealed that his real real identity is Marritza after all.
The Legend Of William Tell The opening credits spoil Drogo's appearance - he doesn't show up until the second episode, and even then he doesn't join them until the very end. Also, Seth, one of the group who breaks out of the mine with Will, isn't in the credits at all, so no one's surprised when he dies saving Aruna. In a more minor example, it also shows Vara laughing and happy with the team, proving that she eventually comes to like them.
Same thing happened in an episode of CSI: Miami featuring Ed Furlong.
The opening used in the Stargate SG-1 pilot "Children of the Gods" was recycled from the movie and didn't show any scenes from the series itself. Which would be a good idea if they also left Christopher Judge's name out to avoid spoiling Teal'c's defection. That is, for those who recognize Christopher Judge as Teal'c.
In one episode while Daniel was dead and Ascended, Michael Shanks appeared in the beginning credits as a guest star. However, it turned out that he was playing his other character, the Asgard Thor. Another episode had Thor make a surprise appearance in the end, for this scene, Shanks was put in the ending credits.
Similarly, after Daniel Descended at the end of that season, the opening credits for the following season included Michael Shanks as Daniel Jackson, but not Corin Nemec as Jonas Quinn. It was not supposed to be revealed until the end of the second or third episode of the season that Jonas would leave SG-1, and events also threw into questions whether or not Daniel would actually stay. Not that the audience really questioned that. Status Quo Is God
Like the above example, the first episode of season nine includes Mitchell, Daniel, Sam, Teal'c and Landry, even though it was (supposed to be) uncertain whether or not Daniel, Sam, and Teal'c would actually come back to SG-1, while Vala was being played as a returning character. The latter was a "special guest star" until about a quarter of the way through the season, and also made opening credits the next year. However, Sam didn't return until several episodes into the ninth season.
Stargate Atlantis did not have a title sequence for its pilot, which would have revealed the plot. Season Two averted this trope by not having a title sequence at all for the first several episodes in, by which time we had discovered who was MIA and who was joining the cast. Too bad they forgot this for the state of Season Five.
Also, there's an easy-to-miss one early in the fourth season of Stargate Atlantis. The show reverts to using the previous season's opening sequence (or the credits in it, at least), including Dr. Carson Beckett, who died around the end of the third season. His name is only in the opening credits for one episode, though, so you can chalk it up to a mistake... unless you've previously read about the "Oh, Michael's got a clone to replace the dead original" thing that's going to happen.
In the fourth season, however, there's one that's very difficult to miss. The third season ended with Elizabeth Weir being injured. In the fourth season opener, Torri Higgenson, who plays Weir, was left out of the credits, as was Paul MacGillion as Beckett, who had died partway through the third season but been left in until the end. Higgenson was replaced by Amanda Tapping as Sam Carter.
LOST did this in Season 6, including Desmond's actor, Henry Ian Cusick in the credits all season, long before his eventual "surprise" appearance.
Although considering the fact that the creators pretty much told everyone before the season started that the actor would be returning, this may have been their way of keeping the surprise of WHEN they were returning rather than THAT they were returning.
Lost has done this several times-someone gets shot and is left for dead, yet remains in the credits. Oh, I wonder if they'll survive! And they once did it with that same actor-the character ran off. Of course, the surprise once again was when he would return. Given this happened at the end of an episode that was otherwise amusing filler, mission accomplished, Darlton.
Though it should be noted that an actor still appearing in the credits of this show doesn't necessarily mean they're still alive, as the dead characters in Lost often show up in dreams/hallucinations or as "ghosts".
Especially after, in season 5, Locke's actor Terry O'Quinn remains in the credits and continues to appear after his death... but then we find out that it's not him and he's been dead all season.
In Season 6, Daniel Dae Kim, Yunjin Kim and Zuleikha Robinson all remain in the credits after their characters are killed.
Kamen Rider Ryuki averts this trope by masking over the eyes of a number of people would would be suspected to be Kamen Riders, if not for the fact that they don't even appear in the show.
It's American counterpart, however, plays it half way. While it spoils all the riders (save for Eubulon/Alternate), it does not spoil the men and woman behind the masks.
Recent Kamen Riders love spoiling the movie(if it's currently airing in theatres) in their openings
Kamen Rider Kuuga was especially bad at this. Pretty much everything appeared in the title sequence 4-5 episodes before its debut in the show.
Kamen Rider Fourze showed all the members of the Kamen Rider Club in the opening since the first episode. Since it's on this trope's page, you can guess that they weren't part of the club when the first episode started. In fact, it takes 10 episodes for all the members to join. (12 if you don't count Kengo joining until he becomes Gentaro's friend).
Kamen Rider Gaim did it too. The riders and Arms had a Debut Queue in the show, and things spoiled in the title sequence include Baron, Ryugen, Zangetsu and Suika Arms.
Super Sentai and Power Rangers sometimes have a habit of putting the Sixth Ranger in the opening credits before he is recruited. This doesn't make much of a difference, though, since the new Rangers' identities are usually pretty damn obvious anyway (due to colours and other reasons).
The first episode of Power Rangers in Space averted this by hiding the identity of the new villain of the season, Astronema, by putting the previous season's villain, Divatox, in her spot in the credits. Divatox did appear in this episode, but only made cameos in subsequent ones. Andros was also absent from the first episode opening credits.
Mighty Morphin' Power Rangers avoided Spoiler Openings by introducing them later, for example series 3 opening from part THREE of Ninja Quest, Alien Rangers from part TWO and things like that.
Power Rangers RPM both averted it and played it straight. While the first opening doesn't quite spoil the facts that Ziggy will become a Ranger and Dr. K is a teenage girl (a very brilliant one, yes, but still a teenage girl), it does spoil Dillon becoming Ranger Black (then again it didn't happen until episode 2). Then, later, it spoils Gem and Gemma being the Gold and Silver Rangers.
In an odd case, when the opening of Power Rangers Lost Galaxy was Mike, it also showed scenes of the Centaurus and Stratoforce Megazords (not seen for another 3 episodes), the Red Capsular Cycle (not seen for another ten episodes), and, most egregiously, Leo's Battlizer, which would not make its debut for approximately twenty episodes.
A minor example: Samurai Sentai Shinkenger: the first episode had the theme song but not the opening credits. Unless you were a (most likely adult) fan who was following the news about it (or the very likely scenario, for Japanese children, watching Go-onger's last few episodes), this preserved the surprise of who would become the non-Red Shinkenger (The theme song was playing after Shinken Red had already henshined).
When the opening for Zyuden Sentai Kyoryuger was updated, it contained everything missing from the pre-movie version...including Daigo's Super Mode, which debuted in the very episode the new opening premiered. Also, the new villain, Endolf, wasn't in the opening. Come episode 29, he gets Put on a Bus.
The Opening Narration of season 6 of Robot Wars sometimes ended up with this as it was played over clips from the upcoming episode and essentially gavea away who'd end up fighting who after round one (probably the worst example of a spoiler in this sequence was asking the question "Will Thermador end up in the pit?" over footage of Thirmador driving into the pit!).
Second-season 24 episodes featuring the returns of Sherry Palmer and Nina Myers featured the actors' names in the opening credits. By the end of the season, they began leaving out returning actors' credits until the reveal.
They did, however, spoil a surprise again in the opening credits of the season 5 premiere. At the end of season 4, Tony Almeida and Michelle Dessler left CTU together to settle down and start a new life, yet in the first episode of the new season, Carlos Bernard is listed with the regulars and Reiko Aylesworth is listed as a guest star. By the end of the episode, Michelle is dead.
In season two, Sherry Palmer left during the 14th episode and was missing from the series for several episodes. She returned in episode 21 in a surprise cliffhanger at the end of the episode. However, her actress was listed in the opening credits, so you knew that Sherry was going to be showing up sometime in the episode.
Heroes: The episode that Rebel's identity is revealed, cast member Noah Gray-Cabey is listed in the opening credits. Long-time fans would recognize that he played Micah Sanders and would then feel free to have a good guess at who Rebel is judging by the ways he has been helping and communicating with the other characters even before he actually appears in the episode.
The opening of the first episode of Farscape avoids doing this by removing the exposition of the plot provided in every other episode.
The revised opening for Season 3 did spoil that Aeryn wasn't dead by featuring her prominently in the opening sequence despite theoretically dying the previous season. However, Stark didn't start to appear in the opening until after he had returned.
The opening credits of the first series of Angel include a brief clip of Doyle's death. But it's not really obvious that's happening until you've already seen the episode.
Angel also subverts this in the episode after Doyle's death by keeping the credits the same. Wesley would not be added to the credits until the following episode.
Angel averts this a little later with the appearance of Julie Benz as Darla in the Season 1 finale. The actress was not credited at the beginning; instead, she's listed as a "Special Guest Star" at the end of the episode. Listing her at the beginning would have tipped off everyone, and it was a great surprise.
And then in the season 5 opener, the opening credits not only conspicuously lack Cordelia and Connor, but proudly boast James Marsters as Spike, including him in virtually every clip of the opening, even though at that moment he's still officially "dead" from the Buffy finale, and he doesn't show up until the last minute of the season premiere.
Averted in the UK version of Who Wants to Be a Superhero?, where for episode one (which shows the auditions for the show) the silhouettes of the chosen thirteen are seen with question marks.
Averted (sort of) in Home and Away where Noah is still credited despite the fact Sarah Lewis shot him dead in the previous episode. This was to hide the identity of who had been shot and only reveal it in the episode. That and Noah does appear in that episode (though it's his ghost and only Hayley can see/speak to him) and the next one. It isn't until after then the credits are altered.
Torchwood averted this fantastically. All the publicity material showed Indira Varma's character to be part of the gang, and she is quite a well-known actor, so everybody was very surprised when she died at the end of the first episode.
Averted for new viewers in a later episode were a alien who implanted himself into the cast's memories, is included in the opening along with the rest of the cast.
Spooks averted the trope in much the same way, by having Rupert Penry-Jones appear in all the publicity for Season 7, including doing extensive interviews, appearing in first place in the titles, in group shots etc. His character was killed off in Episode One, and it was a HELL of a shock.
And yet despite displaying awareness of this, the very next season released a publicity photo of all of the characters at their desks. Or rather Ruth, Tariq but no Jo or Malcolm.
At the end of Season 3 of House, all three of his fellows have either been fired or quit. It's rather hard to believe that they are permanently gone, however, when the opening credits for the first episode of Season 4 not only still lists all three actors, but also still ends with an iconic scene of the fellows walking with House. However, the show then turns this trope on its head by continuing to keep the exact same opening for the next two seasons, without adding the new fellows to the opening credits (even after they are permanently hired and are in roles that would merit opening credits in most shows), and despite Chase and Cameron having fairly small roles all through Seasons 4 and 5.
A notable aversion occurs in the season 4 episode when House tries to guess who Wilson's new girlfriend is. In the closing moments of the episode, House secretly follows Wilson to his date and refuses to move until she shows. Surprise surprise, it's a very unlikely recurring character from the beginning of the season (Cutthroat Bitch, played by Anne Dudek). In all other episodes Dudek's name is listed after the opening credits, but that would've been a spoiler in this case so she's listed first in the closing credits.
Amber's later appearances as a hallucination (season 5) weren't spoiled; Dudek was only credited at the beginning of the episode in the middle of that story arc, not at the beginning nor for her surprise re-appearance at the very end.
Averted in Season 5, where Kutner's hallucinatory return would have been spoiled if they'd "bothered" removing Kal Penn's name from the credits when he left early in the season and Kutner died.
Similarly averted in the second season of Veronica Mars, where Duncan's brief cameo in the season finale, where it's revealed that he ordered the execution of Aaron Echolls, was a surprise largely because he hadn't been removed from the opening credits after he was written out. As if to make up for this, in the third season finale the reveal that Jake Kane is the head of The Castle (Neptune's secret society) is undercut by having Kyle Secor listed as a Special Guest Star at the start of the episode.
Red Dwarf, debatably. Series VII's opening credits feature alternate Kochanski. However, as she was being played by a different actress, she wasn't immediately recognisable.
The opening monologue in the latter episodes of series 6 of Shameless shows the dramatic season-ending Mandy-killing explosion, which somewhat undercuts the suspense of the final episode when Mandy is desperately trying to stop Maureen from lighting a match to blow up her house.
Another British example from Misfits - the opening episode features six teenagers starting their community service on the same day. All of the promotion materials and the opening credits feature five of those teenagers. Guess who gets hacked to pieces with an axe 20 minutes into the first episode! Also potentially with Nathan's 'superpower' - the first few episodes haven't shown his power, and his curiousity over what ability he'll get is a running subplot. Except that the opening credits show animations of everyone's power, including his.
With regard to Nathan's power, the image in the opening credits actually constitutes an aversion of this trope. The title sequence depicts what looks like a wolf shadowing him, which indicates some form of lycanthropy as his power. However, it turns out that Nathan is not a werewolf; he is in fact immortal. The wolf-like creature in the opening sequence is likely a reference to his step-father's condition, or perhaps a symbol of death (a black dog, possibly) and the fact that its claw misses him is indicative of his immortality. Admittedly the image is somewhat ambiguous, but it was probably intended to confuse the audience rather than provide them with blatant spoilers.
In Season 1 of The Amazing Race, the opening titles showed actual locations teams would be going to and tasks they would be doing, making it quite easy to work out whether certain teams were going to make it through to the next leg of the race. Seasons 14 and 15 are the only others to show shots from the season during the credits, and they were only ever shots from the current or previous episodes.
In the "Then" part of Supernatural, before the episode, when they recap the events up until that point, they usually focus on important plot points to that specific episode.
Beastmaster's opening credits specifically refer to the main character, Dar, as Last of His Kind, despite the fact that his girlfriend was from the same tribe. He doesn't become last of his tribe until the first season finale, when said girlfriend gets Killed Off for Real.
Each episode of Cupcake Wars has a customized opening explaining the day's theme, including a shot of the two finished cupcake displays.
NCIS spoils the introduction of two of their main characters: The opening credits for the very first episode features Sasha Alexander, spoiling the surprise of her joining at the end of the episode (it could count as a Late Arrival Spoiler, but it wasn't when the episode first aired), while the opening credits for the fourth episode of season three show Cote de Pablo, before her character is reintroduced and made a part of the team.
The season 2 opening of Prison Break changes the opening credits such that it's fairly obvious which characters won't be returning.
The old series of Doctor Who tended to have issues with spoiler closings in serials featuring the Master in disguise - if they credited Anthony Ainley, people would immediately know which character was secretly the Master. As a result, they took to using bizarre pseudonyms like 'Neil Toynay', which apparently caused some trouble and confusion elsewhere in the BBC. They also, in a slight variation, deliberately wrote a scene for Matthew Waterhouse into the serial immediately following Earthshock so that they'd be able to credit him once more, masking Adric's death.
There was also the slight Spoiler Opening for the third Doctor'sfirst episode, where they went to great lengths to keep Jon Pertwee's face hidden through most of the episode to make the Doctor's new appearance a surprise... despite the fact that Jon Pertwee's face just so happened to be the very first thing shown in the opening credits of the same episode.
The same thing happened for the Fourth Doctor in "Robot". He regenerates in the first minute of the episode, but nevertheless the first shot we see of his face is in the opening titles, wearing the outfit that he has a Costume Test Montage and funny Showing Off the New Body gag before we should get to see it.
One new series episode had a carefully-obscured monster who never speaks in a recognisable voice, and all the clips featuring it are shot from its point of view to obscure its appearance until the time the Doctor first sees it. It's referred to by the ambiguous name "Metaltron" and there's even a careful Red Herring about its nature early on when the Doctor spots a Cyberman head in a glass cabinet (Cybermen being made out of metal). Unfortunately, the title of the episode, shown in massive text at the opening, is "Dalek", which leads to the viewer sitting around waiting for the Dalek to show up.
During the Schloss Einstein title song, short video clips of the major kid characters are played. (The title sequence is the same for all the episodes of a given series.) Sometimes, who is in the title sequence spoils the resolution of a plot line. For instance:
At the beginning of Season 14, we know that Ronja will return to Schloss Einstein because she appears in the title sequence.
Max originally isn't supposed to go to Schloss Einstein in Season 11 – he's just there with the rest of his family, who are dropping off his two sisters there before leaving to spend a year in China. He soon convinces his parents to let him stay and become a student there.
This phenomenon was avoided in the earlier seasons because there were so many major characters who just didn't appear in the title sequence. Nothing but Genre Savviness tells us that Joanna doesn't go home after her first few days at Schloss Einstein in Season 6.
The Season 3 opening Warehouse13 shows Myka and lists Joanne Kelley in the credits sequence while listing Aaron Ashmore as a guest star. It pretty much guarantees Myka's not gone permanently, and Steve is not going to last.
Chuck season 2 episode 2, mentions that it's going to guest star Matt Bomer, who shows up at the end of the episode as a massive surprise! Unless you paid attention to the opening credits.
Even more egregiously, and once again involving Matthew Bomer, was his being listed as a guest star in the opening of the first season episode "Chuck Versus the Imported Hard Salami." At a time when Bryce Larkin is still believed to be dead, spoiling The Reveal that the container Fulcrum was attempting to smuggle in contained the very much alive Larkin.
Fridge Brilliance: At the time, Bryce had already appeared in another episode after his "death," in the pilot albeit only in a flashback. After being credited in this episode as well viewers would likely assume that it would merely be another flashback with him, instead leading to the reveal where he turns out to actually be alive.
The title sequence for MythQuest contains expository information about Gorgos, the antagonist, that wouldn't be revealed until the fifth episode. It makes watching those first few episodes somewhat painful.
In the Season 1 opening of Oz is a shot of someone wearing the mask and restraints of a prisoner about to be executed. Though his face is hidden, we can clearly see a "MOM" tattoo on his hand.
Season one of The Outer Limits frequently had previews of the episode before the opening sequence. These previews often gave away important plot points or the appearance of monsters that the actual episode slowly built up revealing.
Game of Thrones opens every episode with an Emmy-winning, CGI-animated sequence showing a map of Westeros, zooming in on certain cities and towns. The cities shown are major settings for the episode to come and change periodically as new locations are introduced in the story arc. Often, however, the sudden appearance of an unfamiliar location in the opening credits - or the disappearance of a familiar one - has served to telegraph major changes in setting occurring in the episode.
The opening credits in the third season of Series/Onceuponatime both plays straight and subvert this with two characters. At the middle of the season Rumplestilskin dies in a heroic sacrifice but the actor's name still appears in the credits of later episodes. Thus his come back wasn't a big surprise. Then Neal/Baefire dies, the actor's name still appears in the credits... but the character only appears later in two flashbacks.
Many Shakespeare plays spoil the ending in the prologue, which was basically their point. The enjoyment of the story wasn't to be surprised by the outcome, but to see how it gets there. For example, Romeo and Juliet states that Romeo and Juliet die. In fact, many plays are referred to as tragedies right on the title pages of printed editions, so you know that things turn out poorly before you've read a word.
The 2005 stage musical Willy Wonka is a Charlie and the Chocolate Factory adaptation that's Truer To The Text than the 1971 film version but uses its songs. The opening scene takes place in the factory, with Willy Wonka the first character the audience meets, and he goes on to reveal that he's planning to retire, but not before he finds an heir. In the book and most adaptations, he does not appear until the other characters arrive at the factory for the Golden Ticket tour and The Reveal that he's been seeking an heir all along is the climax of the story (he does appear in a few flashbacks in the first half of the 2005 film in order to explain the backstory, but his face is usually obscured and by the time he appears in the second half, he's...changed a bit). While the story is well-known and parodied enough to qualify as It Was His Sled, and Mr. Wonka is the most memorable character in it, this opening not only spoils the whole show, but negates the attempts in subsequent scenes to build up any mystery surrounding Mr. Wonka.
The Chrono Trigger opening, which spoils such events as the Epoch getting its wings. It also shows 1999AD's world erupting and being split apart and Lavos appearing.
The opening of Lunar: Silver Star Story for PlayStation give some spoilers, like Alex turning into a Dragon Master, Nail transformation into a White Dragon and the only party members that will stay with you until the end of the game.
The opening to Tales of the Abyss is littered with spoilers, most notably Asch looking exactly like Luke, Luke fighting Asch, Luke having cut his hair (which is very symbolic in Japanese media), Luke and Natalia being surrounded by soldiers (from the land which Natalia is princess of) and the appearance of the final dungeon, among other things.
Not to mention the theme song itself, which pretty much lays out the relationship between Luke and Asch throughout the entire game, right through the epilogue. Well, it's pretty moot if you don't know Japanese, and the English version took out the lyrics...
Tales of Symphonia did the same thing, wait, is that assassin in a set of shots containing various party members?
Looking at the opening, you also couldn't tell that Regal does a Heel-Face Turn, either.
And why is Lloyd reaching for his sword in apparent opposition to Kratos?
Basically, every scene depicted in the opening actually happens at some point in the game; but without context to put it in, you can't tell what it's about. (Such as Sheena preparing to activate the Mana Cannon.)
The first shot of the opening fades in the image of a blond person in white. It's debateable wether this is Colette or Yggdrasill/Mithos as they look pretty similar.
Pretty sure it's the latter. If only because of the hair.
If you just so happen to be watching the Anime of the game, without playing it, don't worry the openning will helpfully inform you of all the major characters. Not that the show itself is very subtle but still...
It's a series thing. Tales of Phantasia's PSX opening featured Fujibayashi Suzu prominently - she was a minor character in the Super FamiCom incarnation of the game, but had been upgraded to a semi-secret playable.
And in the opening for Tales of Legendia why do we see, among other things, Chloe stabbing Senel?
Tales of Rebirth mostly avoids this, since the opening only shows a) Minor spoilers (Shaorune), or b) Scenes that don't happen in the game (Annie attacking Eugene and Mao blocking it). An exception would be Agarte being listed as one of the good guys, something she doesn't become until 3/4 into the game.
In Tales of Graces if you're at the very beginning of the game during the childhood prologue, the opening contains some major spoilers of what happens after the prologue.
Happens again in ''Tales of Xillia. You get to see Gaius hanging out with the chimeriad... and then the main character (whichever one you pick) fighting Gaius in the rain. It also shows several shots of the characters in a snowy modern city, an end-game location.
Final Fantasy III on the DS has an opening cinematic that show off many of the elements that would appear later in the game, such as the airship and the exterior of the final dungeon. By the looks of it, IV will follow suit. Though, in their defense, the originals had been released, what, seventeen years previously?
In a similar vein, Final Fantasy VI had an FMV cinematic on the PS remake that showed off most of the characters, although it didn't exactly spoil their role in the game. But it did contain some key elements, such as the coin toss between Edgar and Sabin.
This example also some what spoils a major plot twist due to what it doesn't show. Emperor Gestahl is the big bad for half the game before being replaced by Kefka yet he does not get a single appearance in the trailer while Kefka appears in every third scene.
Both the PS and DS remakes of Final Fantasy IV spoil Cecil becoming a paladin and adult Rydia, and the PS version also spoils Palom and Porom petrifying themselves.
Baten Kaitos... well, let us put it this way. If you wish to enjoy the actual plot, hit Start the instant the opening begins.
The opening to Persona 3 spoils a few things if you're paying close attention. Most glaringly, it shows the texts "Remember you are mortal" and "Memento Mori." Granted, it doesn't make sense in context. It's only after you beat the game that you realize it flat out told you the main character would bite it before you ever started playing.
The opening to Persona 3 FES, however, spoils the death of the main character in a subtle-yet-not-so-subtle way. Mainly by showing scenes from The Answer, where Aigis is the main character.
FES has a minor Musical Spoiler in it's opening as well, if you can speak Japanese. The first verse of the theme is sampled from Kimi No Kioku, the ending theme of The Journey. Though it's difficult to interpret the meaning of the song through a single verse, Kimi No Kioku is a song about a person coping with the death of a loved one.
Persona 3 Portable's Opening also has the obligatory spoilers. Memento Mori is still there, but the very last shot of the opening is Minato and the Female Protagonist preparing to use their evokers while a field of Dark Hour Coffins rush by in the background. Just before the final shot, each protagonist aligns perfectly with one of the coffins, looking as though they are resting in them. Of course, anyone whose played the original knows that the new girl is doomed to the same fate as Minato, so it's only a spoiler if you've never played it on the PS2.
Persona 4 has two openings, an animated one which shows clips of all the party members, which isn't so spoilery in itself. The second opening is much more spoilertastic, not only showing Teddie's Shadow and Persona, which isn't much of a spoiler for anyone whose played Persona 3, as the Mission Control character always eventually joins the main party. But it also spoils the fact that Naoto is a Sweet Polly Oliver, by showing her speaking in a clearly feminine voice.
Naoto being playable could have actually been quite the spoiler if it wasn't thrown right in your face with the opening since, unlike other party members who get involved in the plot right before they join, she's the only one introduced a long time before joining and acts as the closest thing to a rival.
The PSP Updated Re-release of the original Persona continues this with the imagery of a head and a town springing from it and the end shot shows Maki standing over the town. The presumed Alternate Universe is just a dream world of hers that's slowly starting to take over.
Like the aforementioned Tales of Symphonia/Persona 3, Neverwinter Nights 2 has a spoiler opening that's rather cleverly masked because it's without any context whatsoever. It depicts Shandra Jerro's ancestor Ammon Jerro (who you're lead to believe was a jolly and kind mage) fighting against the King of Shadows (who you're lead to believe is Ammon Jerro) while using a sword that breaks into numerous silver shards THAT YOU'VE BEEN HUNTING DOWN THE ENTIRE GAME.
But then again, he's in every match as the referee in the background, so no one is gonna guess that this secret character is actually playable.
Fire Emblem: Path of Radiance and Radiant Dawn (the GC and Wii Radiance games) have an opening cinematic of some of the game's plot. While it technically has minor spoilers (e.g. Ike fights the Black Knight, what a shock), everything happens so fast that one is more likely to be confused than spoiled if they haven't played the respective game.
A particularly notable case, in the opening for Radiant Dawn, there's a section showing various characters in the game; one of the characters shown is Renning, Elincia's uncle and former leader of the Crimean Army, who was supposedly killed early on in Path of Radiance. While it was a popular theory that this character was the true identity of Bertram of Daein's Four Riders, him being still alive after you 'killed' him was a plot point that only comes up near the end of the game.
Path of Radiance's intro also clearly shows Leanne, spoiling her survival and the revelation that Reyson and his bedridden father are not the only remaining herons.
Fire Emblem Awakening's intro contains a blink-and-you'll-miss-it spoiler: Near the end of the cinematic, Risen are shown emerging from a Swirly Energy Thingy from the future. Look closely, and you'll see that among them is your future self, travelling back in time.
The very first actually playable part of Awakening counts too. It shows your avatar killing Chrom after fighting Validar. The final fight with Validar takes place in one of the last few levels, though you manage to avoid killing Chrom when this happens for real.
The title screen of Final Fantasy Mystic Quest displays five crystals, four of which are depowered. Avoiding spoilers, the existence of a fifth still-functioning crystal doesn't come up until very late in the story.
The Opening of Space Channel 5 Part 2 gives you the pretty obvious hints of Jaguar being Shadow and Purge being the Big Bad.
Kingdom Hearts comes to mind here. It has a good opening and song to go with it, but you notice certain things, especially when playing the game over. The entire thing seems to be symbolism. You see odd, somewhat creepy looking, white-haired teen holding out a hand as the brown-haired protagonist hesitates and looks somewhat scared. A wave goes to engulf white-haired teen and brown-haired kid runs out finally, trying to help him. The wave crashes down, washing away brown-haired boy, but the white-haired boy is still standing, smirking. This is pretty much telling you that Riku is going to be "evil" and Sora afraid of that darkness. In fact, the scene in the game is almost exactly like this, but there is actual darkness rather than a wave. It also pretty much says who the three original main characters are and who of your friends on the Island won't be appearing again. Kingdom Hearts 2 shows pretty much the entire plot of the previous two games, hot older Kairi in the costume that doesn't appear for about half the game, an odd connection between Kairi and Namine, and connection with Sora and Roxas, for all those people who didn't play the first one or Kingdom Hearts: Chain of Memories or are just getting into the series? Well, there you go, everything told for you and you didn't even have to try. Of course, it somewhat manages to avoid this with a good about of symbolism.
Birth by Sleep does this one straight ANDinverts it. In a typical fashion, the opening is symbolic of the events that transpire (though most of the symbolism will likely go over your head until beating it), but the true spoilers come from the credits. The game is split into three stories, however they can be done in any order. The cast listing reveals Richard Epcar as Terra-Xehanort and Haley Joel Osment as Vanitas. This gets even more ridiculous as the former only appears in Terra's story (not counting the Final Episode), and Vanitas's actor corresponds with his face, which is only revealed in Ven's, so there is no order to play the story in that avoids this. Thankfully the credits are skipable and (apart from the Final Episode's) lacks "Simple and Clean."
The opening to Kingdom Hearts Coded features brief scenes in the beginning of Aqua, Terra, and Ven as of the ending of Birth by Sleep. Each scene is only maybe a second long, but at the time coded came out Birth By Sleep was only about a year old.
Golden Sun's second installment, The Lost Age. Your final party consists of four characters, and the game starts with three playable characters. Based on the elements of the characters in your starting party, you know that the fourth party member has to be a Mercury adept. And, how convenient, one of the characters that is introduced at the beginning of the game is a Mercury adept! You spend most of the beginning of the game chasing him, and nearly everything within the game points to having this fellow as your fourth party member. So it comes as no surprise that, later in the game, the fourth party member is someone completely different, a sailor that the party has never encountered almost up until the moment that he joins. How would one expect this dark horse to be the fourth party member when one of the other characters seems to fit the role so naturally? Well, he appears on the box art, and is shown in several game manual screenshots as part of the party.
In Thief: Deadly Shadows some file names contain spoilers (for example: gamalls_treachery_engl_none_30.bik). They are displayed on the screen during the game installation.
The World Ends with You does this magnificently, in that anyone who has beaten the game will notice that the opening goes through the entire plot. It shows Joshua, the two Shikis, Rhyme's fate (and hints at the reason for her and Beat's deaths), Kitaniji's plan for Instrumentality, the reason for (and place of) Neku's death. Meanwhile, anyone new to the game will simply think it's cool.
In Skies of Arcadia, if you wait long enough on the "Press Start" screen, a different intro will begin to play. Unlike the first, this one consists entirely of actual scenes from the game, many of which are spoilers. Some aren't spoilers unless you know the context, but many spoil huge plot twists that happen fairly late in the game.
Last Battle on the Sega Genesis — a license-less port of Fist of the North Star — gives away the entire plot in the introductary scrawl.
Pokémon intros tend to give away little things you should know if you watch the commercials or look anywhere on the box. However since Platinum they have been giving away the villains.
Done cleverly in Pokémon Ranger: Guardian Signs: Lugia's silhouette can be seen looming in the background of the opening cinema, but is quite easy to miss.
Hyperdimension Neptunia spoils us in the opening sequence when a jet comes by while Neptune is being shown. Most of us would said Cool Ship already if it weren't for the fact that later on, Neptune herself transforms into that jet plane for one of her attacks.
The opening of Nier is chock full of spoilers, revealing, among other things, Weiss's connection with the Shadowlord, Kaine's half-Shade nature, Fyra's death, and the Twins' betrayal. All in a montage set to the final boss theme.
The opening to the console version of the first BlazBlue game heavily implies that Hazama isn't just another NOL officer. The arcade version of Continuum Shift's opening all but flat-out states that he's a major villain. Later, the opening to Continuum Shift II hints at Litchi's Face-Heel Turn, and depicts Noel turning into Mu-12.
If you don't want to be spoiled on some of the mechs and battles in Vanguard Bandits, you'd better not watch the Openings.
Also, the title screen clearly shows Adult Link riding Epona.
The UK special edition/pre order box art for The Legend of Zelda: The Wind Waker has to be the most ridiculous example of this ever, because it features the final boss battle on the front cover. Keep in mind that at the start of the game, you technically don't know Ganon is in it, don't know Tetra is Zelda, don't know the Light Arrows exist and don't know about flooded Hyrule. Here's the artwork in question: The Wind Waker box
The Legend of Zelda: Twilight Princess does it too, in an artwork in the instruction manual. Alongside the main characters, you can see Zant and an unknown young woman. Zant is revealed relatively early on, so it's not much of a spoiler, but the young woman is a spoiler: That's Midna's true form.
Deus Ex. It doesn't get more spoilery than seeing a fellow augmented agent and the Big Bad discussing their plan.
Project X Zone is egregious with this example. You see a Humongous Mecha during the opening after the city was blown up. For awhile, you don't seem to see the guy till the intermission where you finally get all your units and supports. It's then revealed that he's the Final Boss.
The opening video in Sonic Adventure spoils Chaos's final transformation and the destruction of Station Square, which are events that don't occur until the end of the game. Rather creepy to think that before you even start the game, you know almost every person you meet will die by the end of the game.
Each time you start a new game in Little Busters!, you are shown a pretty cool opening video for the game displaying many beautiful CGs. The problem is that a lot of them are from late in the routes and so implicitly or explicitly spoilery.
The opening for Corpse Party spoils among other things Seiko's death by hanging.
In Dangan Ronpa's opening movie, a few brief images of Leon's execution are visible.
In Monster Hunter Tri, The Stinger at the end of the trailer shows a gigantic serpentine monster at a lake letting out a low-pitched roar. Said monster is Dire Miralis, the final boss of the game's Online mode.
Final Fantasy XIII: The opening ends on Vanille, alone, standing looking at Cocoon hanging in the sky above Pulse. This spoils the fact that yes, you will eventually get to leave Cocoon and go to Pulse. What it doesn't spoil is the subtle hint behind Vanille being alone in this scene; she is from Pulse, unlike the others (except Fang).
Valkyria Chronicles, After showing Selvaria in combat in Valkyria form several times throughout the intro, it then shows a close up of Alicia in Valkyria form, so short and close up that those who havent played the game would assume it was Selvaria again ''.
The first season of Justice League Unlimited showed clips from the current episode during its opening, occasionally spoiling plot points.
Likewise, an animated Funny Animal version of Adventures Of Oliver Twist features a montage of all the plot points from an episode, from beginning to ending, put just before the episode begins.
Legion Of Superheroes pilot 'Man Of Tomorrow' had spoilers in the opening credits, showing Timber Wolf who wouldn't be making an appearance until the next episode.
Kim Possible: Lord Monty a.k.a. Monkey Fist appears in the opening theme from the very first episode onwards, however his first appearance was not until episode 13, where it was written as if Monty turning out to be the bad guy was a big twist.
This happens again in the last season when the Opening changed, spoiling Warmonga well before her episode appearance. Once more her episode is written as if we're not supposed to have any idea who this other green skin lady who's helping Drakken who isn't Shego was.
Twilight Sparkle:I used to wonder what friendship could be / Until you all shared its magic with me.
The Japanese dub opening sequences, however, runs with the trope; the 3rd opening spoils the CanterlotWedding.
The intro for Gargoyles is comprised of scenes from the show's Pilot Movie, which causes problems when you're watching it as a five-part episode.
Exo Squad: The opening narration talks about a war between the Neo-Sapiens and the Humans... a war which only STARTS in the sixth episode. This is made all the more confusing by the fact that that a Human/Neo-Sapien war took place in the show's backstory (but not the war the opening narration shows clips of).
Family Guy somewhat subverted this in their two part special "100th episode". The title of the first part, "Stewie Kills Lois", spoils the plot point near the beginning where Stewie does just that. The conclusion's title, "Lois Kills Stewie", not only spoils Lois's return, but also the apparent resolution of the episode. But when that moment actually came, it was Peter who killed Stewie. Not that it matters anyway, since it was all just a simulation.
The intro to X-Men: Evolution shows all of the X-Men gathered together and shows them off by name, despite the fact that half of them don't show up for several episodes. The most notable case is Rogue, who is introduced early on as a character, but keeps her allegiance uncertain until halfway through the season.
Episodes will often open with a recap of anything from an earlier episode that is related to the current one in any way; if scenes from the episode "Jet" shows up in the recap, don't be surprised about the character Jet suddenly showing up in the episode. The Order of the White Lotus was given obvious importance extremely early because of this, for one example.
An alternate opening narration for the first episode averts this trope, as it gives more information on the war and the Avatar but doesn't mention Aang. Before long, though, the opposite problem develops, as the narration becomes wildly outdated by the end of season 1.
The theme song for Total Drama Action features Courtney, who came back halfway through to the surprise of the castmates and (maybe) Chris. However, the flipbook itself had no intention of this ever being a spoiler.
The leaked theme song for World Tour also FINALLY settled the issue of Ezekiel's participation in the season or not. He's in. For now.
The Japanese opening of Transformers Animated spoils Longarm being a Decepticon, Blackarachnia commanding the Dinobots, and Starscream's Allspark fragment and clones. However, there's also so much stuff that simply doesn't happen that it's hard for a new viewer to tell what's important and what isn't.
A lot of characters that don't show up until the second or third season are given a lot of prominence.
Despite being introduced as Shredder's lieutenants, Chris Bradford and Xever are strangely absent from the intro of Teenage Mutant Ninja Turtles (2012). Instead, Shredder is shown standing with the mutants Dogpound and Fishface. No prizes for guessing what's going to happen to Bradford and Xever.
An episode of the animated Young Justice series has the team helped out by an arrow fired from the shadows. When they confront Green Arrow and accuse him of babysitting them and he proves it wasn't his arrow, they assume his sidekick, Speedy, is ready to join the team after storming out in the pilot. Yeah ... or maybe it's the female archer who appears in the opening credits of the show as a team member despite having not appeared in the actual show yet at that point.
The team isn´t completely assembled in story before episode 6 but the intro shows the whole team since episode 1.
Similar to the aforementioned Justice League Unlimited series, right before the show's logo is viewed, each Young Justice episode's opening contains a quick display of clips which previews events that occur later in whichever episode is airing at the moment which is at least less spoilery because of the rapid speed the images flash on the screen.
In ReBoot every four episodes of season 3 had an opening sequence using clips from those four episodes. Naturally plot developments like Enzo's Time Skip, the Saucy Mare's web armor, and Mainframe in ruins are spoiled. Averted with the Toonami broadcast, which replaced those openings with customized ones.
The opening credits for The Secret Saturdays features the Saturdays being charged by a quartet of villains. While one of them, Piecemeal, shows up relatively early in episode 4, the others are Eterno, a one-shot villain who doesn't show up for several more episodes, Rani Naga, who also doesn't appear until almost the end of the season, and Shoji Fuzen, who appears in episode 3, but is wearing blue samurai armor he won't don until many episodes later.
Even before Valmont and his three last Enforcers (Finn, Ratso and Chow) met Daolon Wong, Season 3 intro revealed the Enforcers becoming Wong's Dark Chi Warriors and it did not feature Valmont, revealing the latter wouldn't appear as often as he did the previous story arcs.
Season 4's first episode started with a Previously On showing scenes from when people other than Shendu controlled Shadowkhan and scenes from when Daolon Wong was depowered. Before the intro, Wong tried to regain control of Shadowkhan to make them break him out of prison but he instead awakens Tarakudo. Then the intro shows Tarakudo as that season's Big Bad, the Enforcers working for him and Wong not being featured.
Season 5's intro doesn't feature the Enforcers and, while Drago becoming the major antagonist was probably expected by the time the intro first started, his featured henchmen wouldn't appear before his third episode.
Adventure Time. Just pay attention to the first 5 seconds of the opening, and you will get spoiled with one of the biggest plot twist in the whole series-The fact that Ooo is actually the remains of Earth after a giant nuclear war.
The Avengers: Earth's Mightiest Heroes shows in its original intro that yes, Captain America survived getting thrown into an icy sea. His debut episode tried to make it seem ambiguous. It also shows Hank Pym becoming Giant-Man, an ability he doesn't demonstrate until his second appearance (chronologically speaking) Additionally, episodes set before the founding of the Avengers show eight members in the intro's Team Shot, revealing that Hawkeye won't remain an enemy of the heroes for long.
The fourth season of Flander's Company has Clara appearing in the credits along the other employees, completely spoiling both her return and her Heel-Face Turn.