Okay, so we have no idea how the Marvel Brain Trust decides on which real-life people to allow inside the MCU, because what follows is one of the weirdest lists of celebrities you're ever likely to encounter. Not all of them are cameos – they might exist only as a casual reference.
It's such an odd group, though, that only one of the following was deemed significant enough to earn a place on Steve Rogers' post-freezer catch-up list.
The rest, well, see for yourself...
1. Hugh Hefner (Iron Man)
Stan Lee's first MCU cameo set the standard for every single appearance that followed – each one has miraculously fit the tone of the film it's in.
In Iron Man, the comics legend is mistaken for Hugh Hefner, the late Playboy entrepreneur. With Stark being less James Watt and more James Bond in the first Iron Man movie, it makes sense that the Playboy Mansion exists in this universe – it's a place we're sure Stark has visited frequently.
It does feel weird that the opening salvo of a family franchise features a gag about a pornographer, but y'know, that's Disney for you...
2. Kevin Bacon (Guardians of the Galaxy)
"On my planet, there's a legend about people like you," Star-Lord says in the first Guardians. "It's called Footloose. And in it, a great hero, named Kevin Bacon, teaches an entire city full of people with sticks up their butts that dancing, well, it's the greatest thing there is."
That's a line that throws the entire MCU into chaos.
The 'Six Degrees Of Kevin Bacon' rule – which says that all actors are only six people (if that many) away from being in a film with Kevin Bacon – confirms that Star-Lord is in fact not played by Chris Pratt, but actually IS Chris Pratt (Pratt appeared in Movie 43 with Emma Stone, who appeared in Crazy, Stupid, Love with Bacon).
That means we're only a few films from an Avengers movie in which the plot revolves around all our favourite heroes (including Thanos – as Josh Brolin appeared with Bacon in Hollow Man) realising they're only actors appearing in a highly successful film series. And they have a limited time to get profit share deals before the credits roll.
Still, Kevin Bacon's happy.
"Whether I was mentioned in the movie or not, in my opinion it was one of the best movies of the year," Bacon says. "I loved it. And I didn't talk to anybody who didn't love it."
In terms of other real-life folk, Guardians also features a Jackson Pollock sperm gag, and a spaceship named after Charmed star Alyssa Milano.
3. Leonardo DiCaprio (Ant-Man)
Luis: How serious are we talkin', Scotty?
Scott Lang: [Looking at a safe] It's a Carbondale. It's from 1910, made from the same steel as the Titanic.
Luis: Wow. Can you crack it?
Scott Lang: Well, here's the thing, it doesn't do so well with cold. Remember what that iceberg did?
Luis: Yeah man, it killed DiCaprio.
So, this Ant-Man dialogue explains why Leonardo DiCaprio will never do a film in the MCU.
That's because it's confirmation that in the MCU, Leo's a movie star – which means he can't just pop up to play Mr Fantastic or whoever.
It just wouldn't work to have dialogue like 'Hey, aren't you Leonardo DiCaprio?' with a reply along the lines of 'No, I just really, really look like him' every time Mr Fantastic walks into the room.
No, DiCaprio will have to stick to showing up in DCEU movies, which, as we all know, are what people in the MCU go to the cinema to see.
4. Elon Musk (Iron Man 2)
"It's not based on him, it's based on the comic book," Favreau said when asked if Tony Stark is based on Elon Musk. "But Robert Downey, when we were prepping Iron Man, said, 'There's somebody we should sit down and talk with'.
"[He] said, 'This is a guy who can give us some insight into what it'd really be like to be Tony Stark'."
Musk also helped the crew out by letting them use his company Tesla as a location for the film, so Favreau and his team stuck him in the film to return the favour, with a gag about Tony helping him out with an electric jet.
It's currently unconfirmed if that sports car Musk launched into space was part of the jet's development process.
5. George W Bush / Barack Obama (The Winter Soldier)
Yep, we know there are at least two real-life Presidents in the MCU, thanks to a stack of books in The Winter Soldier. But that leads to some problematic timey-wimey stuff (it's not as if the MCU has ever had that issue before).
That's because Matthew Ellis was President in Iron Man 3 and Winter Soldier. Those films took place in December 2012 and April 2014, which means that Obama didn't serve a second term in the MCU.
It's as yet unconfirmed if Captain America allowed Donald Trump to be elected, but we have to say the chances aren't high.
6. Steve Jobs (The Winter Soldier)
In another potential plot hole, Apple founder Steve Jobs exists in the MCU, which makes Tony Stark's insistence on either using a Vivo phone that's only available in China, or a flip phone that's only available in the past, even more baffling.
Okay, the flip phone thing makes sense because it was given to him by fuddy-duddy Steve Rogers, but someone needs to gift Tony a nice iPhone next Christmas to replace his Vivo device, if he's still alive after Avengers: Endgame to receive it.
Steve Jobs is the only real person named on Steve Rogers' catch-up list, which also includes The Beatles and Nirvana – but they could include anyone in the Marvel Universe, so we're not counting them.
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Sam is an entertainment writer with NCTJ accreditation and a twenty-year career as a film journalist.
Starting out as a staff writer at Total Film, moving up to Deputy Online Editor, Sam was responsible for Total Film’s YouTube channel, where he revolutionised the magazine’s approach to video junkets, creating influential formats that spread to other outlets.
He’s interviewed a wide range of film icons, including directors such as David Lynch, Quentin Tarantino, Paul Thomas Anderson, Sofia Coppola, Ridley Scott, Michael Bay and Sam Raimi, as well as actors such as Meryl Streep, Nic Cage, Brad Pitt, George Clooney, Anne Hathaway, Margot Robbie, Natalie Portman, Kermit the Frog, all of the Avengers and many more.
Sam has also interviewed several comic creators, including Stan Lee, Alan Moore, Grant Morrison, and he has a zombie cameo in The Walking Dead comic.
In 2014, Sam went freelance, working directly for film studios including Warner Brothers, 20th Century Fox and Disney, as well as covering red carpet events for film marketing company PMA Productions.
Sam is the co-host, producer and editor of the Arrow Video podcast, which has seen year-on-year growth since its creation in 2017, gaining over half a million listens in that time.
His byline has appeared in outlets such as Yahoo, MTV, Dazed, Esquire, Harper’s Bazaar, Cosmopolitan, Elle, and Good Housekeeping among others.
In 2012, Sam made it to the final of the Leicester Square Theatre New Comedian of the Year competition, and went on to become a filmmaker himself, directing three features that have all played major festivals, and secured distribution – starring in two of them.
Jim Carrey once mistook Sam for Johnny Cash, and John Carpenter told him to ‘Keep up the good work.’ He promises to try his best.
