Continuity Lock Out / Marvel Cinematic Universe

The Marvel Cinematic Universe did a fairly good job averting this at first, throwing in Easter eggs for comic readers without making it confusing for others. However, as the franchise expanded into television and tie-in comics, and plot lines intersected to a much greater degree, it's become its own tangle. This article warns that this trope might happen to the franchise if it expands itself too much too quickly.

MCU Films

• Hawkeye's appearance in Thor. Non-comic fans and those not viewing it in the franchise's original release order will be left clueless as to why the film stops cold for five minutes to bring in a big name actor to play a random wisecracking guy with a bow and arrow, who never appears in the film again, though this made sense when The Avengers came out.
• The Avengers: The film generally works if you haven't seen all the individual movies beforehand, as long as you've got a rough idea of who everyone is (e.g. Steve is a Fish out of Temporal Water, Thor is a Norse god with an almighty hammer, etc.), but if you want to understand how each ended up in the situation they're in at the beginning of the film (i.e. Bruce Banner in South America, Thor being present on Earth to begin with), you'll need to watch the prior films. Hell, the whole reason for the film's setup (the Tesseract on Earth and Loki's interest in it) is only known if you've watched Thor and seen The Stinger.
• During production on Avengers: Age of Ultron, Joss Whedon said that he wanted to make sure it was accessible enough that it could be understood even if you'd only ever seen the previous Avengers movie. This proved to not be the case, as there are cameos (some of which are very relevant to the plot) from characters that had previously only ever appeared in non-Avengers films, and a key plot point involving the Infinity Stones really only makes sense if you've seen Thor: The Dark World and Guardians of the Galaxy.
• Prior to the release of Captain America: Civil War, The Russo Brothers stated that they'd made the film on the assumption that most of the audience had already seen the previous Marvel movies. It shows. The movie is virtually incomprehensible unless you've not only seen the previous two Captain America movies (though that should be obvious since they're in the same series), but the previously mentioned Age of Ultron as well. Certain key scenes also rely on the audience having knowledge of Iron Man 3, Ant-Man and The Avengers. In an example of Tropes Are Not Bad, many critics and fans praised the way the film applied this trope to Spider-Man. The movie doesn't explain his origin or reveal too much about his backstory, as there was an unspoken assumption that most of the audience already knew the character from any of his previous five movies or numerous TV shows.
• Quite a number of things in Thor: Ragnarok will make more sense if you've watched the previous Thor movies and Avengers: Age of Ultron beforehand. Otherwise, you won't really understand why Thor and Loki's relationship unfolds as it does in the movie and Bruce Banner's own subplot in the movie.
• Avengers: Infinity War broadly assumes that the viewer has seen all of the previous MCU films, as it's chockful of nods and references to prior incidents in the timeline. However, it most specifically requires that the viewer has seen the previous Avengers films (to know that Thanos is involved as the series' Big Bad), the first Guardians of the Galaxy (as the main team and the Collector are present), Captain America: Civil War (as Infinity War begins with several team members on the lam after being broken out of The Raft at the end of the previous film, and heavily involves Spiderman and Black Panther who were introduced in that movie), Thor: Ragnarok (which explains why Thor, Loki and Hulk are on the Asgardian ship) and Black Panther (which sets up Wakanda, the setting for the film's climax).
• Avengers: Endgame takes this even further, as it requires that the viewer is familiar with the two films that came out in between it and Infinity War, Ant-Man and the Wasp and Captain Marvel (2019), on top of having to know about every other film that came before both, especially because the film has the characters time-travelling to various points in their history, such as to the climatic battle of The Avengers and the beginning of Guardians of the Galaxy, and the final battle at the end has every surviving ally and supporting cast of the Avengers show up to help them fight Thanos and his forces (which also include within their ranks the several different races shown in prior films). And as demonstrated when someone who hadn't seen any of the past movies writes his impressions, characters are rarely even called by their names\codenames, so it's pretty clear the movie expects you to know everyone who shows up on screen.
• Spider-Man: Far From Home specifically evoked this trope in a preroll with Tom Holland before certain teaser trailers, in which he recommends viewers to have watched Avengers: Endgame before watching as said trailers spoil plot elements from that film, mainly the death of Tony Stark and the fallout from it.
• Happens in the trailer for Captain Marvel (2019), which features a scene of Carol punching an old woman on a bus with absolutely zero context. Comic book fans and people who've been following the movie automatically assumed the woman was a Skrull (an evil race of aliens capable of shape-shifting) despite the fact that the trailer doesn't even mention them. It took until the second trailer for the Skrulls to show up and the woman to be shown fighting back against Carol.
• Spider-Man: No Way Home takes this even further as it takes elements from entirely different franchises as not only that movie assumes you've watched every MCU film up until Spider-Man: Far From Home, but also Sam Raimi's Spider-Man Trilogy, as well as Marc Webb's The Amazing Spider-Man Series. And Daredevil is brought into canon through Matt Murdock himself showing up as Peter's lawyer (even showing off his Super-Reflexes). Additionally, The Stinger assumes that you are familiar with the Sony's Spider-Man Universe films Venom and Venom: Let There Be Carnage, with the stinger of the latter film showing Eddie and Venom getting sucked into the MCU. Said stinger also shows that Eddie and Venom have spent their entire stay in the MCU getting caught up on everything that's happened... and by the time they're all caught up, they're instantly sucked back into their reality.
• Doctor Strange in the Multiverse of Madness
  • This film not only presumes that you've seen the first season of WandaVision (given how Wanda references the events that happened "in Westview"), but the film itself acts as a pseudo-epilogue for the series, following up on a plot thread where Wanda Maximoff is trying to find real versions of the children she manifested in Westview, and runs into conflict with Strange and America Chavez in the process.
  • In a broad sense, the film presumes that the viewer is familiar with the X-Men (specifically, the original film trilogy from 2000-2006, via the inclusion of Professor X [Patrick Stewart]), "Captain Carter" (a version of Peggy Carter from What If…? (2021)), Captain Marvel (2019), Black Bolt and Reed Richards.
  • Even seasoned Marvel Studios fans who watched all the films as well as WandaVision have complained about Wanda's seemingly sudden villainous turn. However, for viewers of Agents of S.H.I.E.L.D., specifically Season 4, it is in no way a surprise, and makes perfect sense. That's nearly 15 hours of the middle of a television show's run that shows in greater detail the corruption of minds that use the Darkhold, whereas in this film it was shown by implication.

Netflix / ABC / Disney+ MCU Series

• General:
  • For a time, this was the given explanation for why none of the characters from the ABC or Netflix TV shows (Agents of S.H.I.E.L.D., Daredevil (2015), Jessica Jones (2015), Luke Cage (2016) and Iron Fist (2017)) appeared in the movies, even the ones involving Crisis Crossovers. The movies generally have a wider audience than the TV shows (and are released in certain countries where the shows don't even air), and the creators don't want to have to spend time explaining who the hell these people are for the benefit of audience members who might not be familiar with them. However, incidents that occurred in the MCU films influenced events on the Netflix shows, such as the Chitauri attack on New York (in The Avengers (2012)) influencing public perception of street-level heroes like Daredevil and Jessica Jones, while certain characters (like Justin Hammer from Iron Man 2) influenced events that took place on Luke Cage (2016) and other shows.
  • As Phase Four commenced, the previous executive policy for not bringing television characters into other mainline works weakened, culminating in Matt Murdock (Daredevil) appearing in 2021's Spider-Man: No Way Home, while the Kingpin (from the same series) wound up being the final villain of Hawkeye's first season.
  • The Marvel shows on Disney+ serve as a continuation of plotlines introduced in the movies, meaning you have to have seen the movies to know what's going on. And unlike previous shows, characters introduced on Disney+ do appear in the movies, meaning Marvel is no longer concerned with keeping the big screen and little screen separate. The network attempts to address this with Marvel Legends, which briefly gives the backgrounds of important characters and plot elements, but even this is more for the benefit of people who've already seen the relevant movies but simply need a refresher.
• Edwin Jarvis from Agent Carter appears in Endgame, if only because there's a past justification (Tony's J.A.R.V.I.S. AI had to be named after someone) and a production one (that series was created by the ones who wrote the Captain America movies and then the third and fourth Avengers, so it's their character in a way).
• Agents of S.H.I.E.L.D.. Although it's not mandatory to have seen all of the Marvel Cinematic Universe movies, there's quite a bit in this series (Coulson's resurrection, the events of the episode "Turn, Turn, Turn", etc) that makes a lot more sense if you've seen the movies. Also, if you do plan on watching the movies, do that first, otherwise they'll be spoiled (especially Captain America: The Winter Soldier).
  • This trope is why Whedon says the actual agents themselves have yet to appear in any of the films. He claimed that providing a satisfactory storyline featuring the Avengers learning that Coulson is still alive and running S.H.I.E.L.D. would essentially hijack the story and distract from the actual plot.
• Likewise, the Netflix shows are independent of the movies, but it's important to consider that the events of The Avengers (2012) are responsible for a number of things happening in them (like Wilson Fisk profiting off the reconstruction contracts in Daredevil (2015), or an "Incident" survivor in Jessica Jones (2015) becoming a fantastic racist who tries to kill Jessica just because she's gifted).
• While one can go straight from Daredevil (2015) Season 1 to 2 without first watching Jessica Jones Season 1 (in which case, the only thing that might be confusing is Jeri Hogarth's cameo in the Season 2 finale, and a few off-hand references), one has to watch The Defenders (2017) before going to Season 3 since The Defenders ends with Matt being presumed dead.
• The first season of Luke Cage (2016) essentially requires watching Season 1 of Jessica Jones (2015) as that show introduced Luke and many plot points that are of relevance in Luke's own show (such as Reva's death and his past). To a lesser extent, the first two seasons of Daredevil (2015) are also a prerequisite, if one is to make sense of who Blake Tower and Turk Barrett are. The second season, meanwhile, has The Defenders has a prerequisite because Misty Knight loses her right arm in that show.
• Mostly averted with Iron Fist (2017), that serves as an alternate introduction to the evil organization known as The Hand if viewers missed how they first appeared in the second season of Daredevil (even if there's a Call-Back to that said by Claire Temple, the only character present in all the Netflix series). The second season doesn't require having seen Luke Cage Season 2 beforehand even with the addition of Misty Knight here, since The Defenders made clear Danny was going to pull strings to get Misty her bionic right arm (which happens on-camera in Luke Cage S2).
• The Defenders (2017) is the Netflix equivalent of The Avengers, but requires much more backstory, given characters from all the four series show up. In general, the second season of Daredevil and first season of Iron Fist are the main prerequisites since those are the seasons that introduced the Hand, but the first seasons of Jessica Jones and Luke Cage are somewhat also prerequisites to be acquainted with Jessica, Trish, Malcolm, and Misty.
• WandaVision has a cross-franchise one, as a guy who appears claiming to be Wanda's dead brother might solely confuse viewers akin to Darcy saying "she recast Pietro?", or if they’ve seen Age of Ultron, leave them wondering why he's suddenly being played by Evan Peters instead of Aaron Taylor-Johnson... unless they were familiar with the X-Men Film Series, as that is the version of Pietro that Peters played in those movies, making for a startling meta joke.