Avengers: Infinity War will soon be arriving in theaters, and when it does the feverish anticipation and speculation will quickly shift focus to Marvel's next big team-up movie: Avengers 4. Made all the more intriguing by its lack of a subtitle, the fourth Avengers movie will feature a scene that includes "everyone," according to Bucky Barnes actor Sebastian Stan. The scene features so many major actors, in fact, that it took months of planning to bring it together in a way that would work with everyone's schedules.

Needless to say, we're already fascinated by the idea of a scene that draws together characters from all corners of the Marvel Cinematic Universe, and the question of exactly which characters are included in the umbrella of "everyone." Infinity War already features a staggeringly massive lineup, so Avengers 4 - which is being directed by Infinity War's Anthony and Joe Russo - will have to go really big in order to up the ante. Here's everything we know so far about that scene, who'll appear in it, and who might not.

• This Page: When Does It Happen & Who's In It?

The Big Scene Definitely Takes Place in Avengers 4

This might seem obvious, but given that Avengers: Infinity War and Avengers 4 were filmed back-to-back, it can sometimes to difficult to parse which of the movies actors are talking about in interviews. The big giveaway for the 'every character' scene is the fact that Stan confirmed Michelle Pfeiffer is one of the actors appearing in it. Pfeiffer hasn't yet appeared in the MCU, but will make her debut in Ant-Man and the Wasp (the movie immediately after Infinity War) as the original Wasp, Janet van Dyne. Stan also said that Samuel L. Jackson, who plays Nick Fury, will appear in the scene. As far as we're aware, Fury isn't set to appear to appear in Infinity War, but he was on set for Avengers 4. While Infinity War has amassed an impressive number of superheroes (and their friends), it certainly looks like Avengers 4 will offer the biggest union of characters yet - including characters that we've still yet to meet.

Related: Massive' Infinity War Features At Least 76 Characters

It Includes Heroes We Haven't Met Yet

Barring a surprise post-credits sequence, Brie Larson's Carol Danvers a.k.a. Captain Marvel won't be making an appearance in Infinity War, but she will be starring in her own solo movie next year, before Avengers 4 arrives in theaters. Once she's had her big introduction into the MCU, Captain Marvel will go on to appear in Avengers 4 - as Thanos actor Josh Brolin recently confirmed. As previously mentioned, Michelle Pfeiffer's Wasp will also be making an appearance in the big group scene - possibly even in her original armor, since Hank Pym (Michael Douglas) built a brand new suit for their daughter, Hope van Dyne (Evangeline Lilly). According to Sebastian Stan, Douglas will also be featured in the 'every character' scene, making it quite the family affair. For a more complete picture of exactly which characters will be included, however, our best clue may be the huge tenth anniversary cast photo that Marvel released earlier this year.

It Took Months to Organize

Three months, to be exact. "I can't really talk about that scene," Sebastian Stan explained cryptically. "But I knew it took them three months in planning this scene to have everyone there." Principal photography on Avengers 4 wrapped a few weeks before Brie Larson had to start work on Captain Marvel, but one of the bigger challenges may have been working around Ant-Man and the Wasp, which was being filmed more or less concurrently with the fourth Avengers movie. Samuel L. Jackson's commitments may also have proven tricky, since he began work on M. Night Shyalaman's Unbreakable/Split follow-up Glass in fall 2017 - right in the middle of Avengers 4's production schedule.

Playing an MCU superhero - or even a supporting character - is a fairly big commitment, but since most characters go a few years between solo movies, Marvel actors tend to stay pretty busy with other projects. Last year, for example, Stan and Jackson worked together on the war film The Last Full Measure. Even Spider-Man actor Tom Holland, who by the end of 2019 will have appeared in five different MCU movies in the space of four years, managed to squeeze in filming a lead role in Doug Liman's sci-fi adaptation Chaos Walking last fall - again, a commitment that may have presented quite a challenge when it came to coordinating Marvel's big team-up scene. Basically, this scene sounds like a coordination nightmare - though hopefully one that will pay off.

It May Have Been The Day Of The Class Photo

The actors of the MCU are busy people, and getting all of them together in one place is no mean feat - but it's a feat that Marvel Studios pulled off with the tenth anniversary photo shoot. This "class photo" featured 79 people - a mix of actors, directors and producers from a decade's worth of Marvel movies. Now, it's unlikely that every single actor who appears in this photo is going to appear in Avengers 4 (among them are actors who played now-deceased characters, and others who played minor villains like Crossbones and the Grandmaster). However, it does make sense that, if Marvel went to the trouble of corralling a massive collection of Marvel actors for a particular scene in Avengers 4, and it took three months of planning to get them all in the same place at the same time, the studio would have booked this photo shoot in for the same time.

Certainly all of the named actors - Samuel L. Jackson, Michelle Pfeiffer, Michael Douglas and Brie Larson - appear in this photo, along with others like Cobie Smulders (Maria Hill) and Emily VanCamp (Sharon Carter) whose characters could very well return for one big all-out battle in Avengers 4. The biggest omission from the cast photo is Josh Brolin, who plays cosmic big-bad Thanos, but the Russos could feasibly shoot a big team scene without him, since he plays a CGI character. We don't know the context of this scene, after all; maybe Thanos isn't even in it.

With a mega-franchise as huge as the MCU, and the Avengers movies at the center of it, the pressure is on to make each movie bigger than the last. As Avengers: Age of Ultron demonstrated, sometimes that pressure doesn't always work out for the best. Ultimately, regardless of how many characters the Russos managed to wrangle for this scene, what really matters is the story that will bring them together, and how it's executed. Let's hope it lives up to the hype.

More: Every Character Confirmed For Avengers 4