The directors of the Marvel Cinematic Universe have been known to cram as many characters, celebrities, subtle references and easter eggs as possible in a movie. Every time an MCU movie comes out, you can count on tons of videos and articles listing everything that you may have missed while watching the movie. Even though, most of us try to catch these easter eggs ourselves, keeping up with all the references to the comics, other Marvel movies and pop culture in general is no easy task. Easter eggs and cameos can be incredibly well hidden, and thus, difficult to spot, so we're all bound to miss something.

For this list, we focused our attention on the many cameo appearances that have taken place in the Marvel Cinematic Universe. These are usually brief appearances, sometimes voice parts, or non-speaking roles featuring celebrities, movie directors, talk show hosts, musicians -- well, you get the idea. Every MCU movie, of course, includes the obligatory Stan Lee cameo, but most directors won't stop at that. James Gunn, the Russo Brothers and Jon Favreau are all known for incorporating as many cameos as possible in their movies. Whether it's a comic book author, a close friend of the director from another project, or a seemingly random celebrity the MCU directors are absolutely crazy about these inside jokes. And we're enjoying them just as much. Given the sheer volume of cameo appearances in the MCU, choosing our favorite ones was a daunting task, but we've managed to get it down to 30.

30 KATE MARA (IRON MAN 2)

Kate Mara as a US Marshal in Iron Man 2 in the MCU

Iron Man 2 is packed to the brim with easter eggs, references and -- yes, you guessed it, cameos. Kate Mara made a brief appearance as the US Marshall who waits for Tony in front of the Expo to hand him the subpoena.

As it happens, Kate Mara would go on to star in a Marvel movie herself: the 2015 Fantastic Four reboot. Unfortunately, that movie was a complete flop and stands as one of the worst superhero films ever made.

29 BILL MAHER (IRON MAN 3)

Comedian and satirist Bill Maher is currently hosting the Real Time with Bill Maher talk show on HBO. The hour-long program airs on Fridays with Maher and his guests discussing current events in the news and media.

In Iron Man 3, Bill Maher appeared as himself hosting Real Time With Bill Maher, making a satirical comment about War Machine's new paint job. But, he failed to observe that Colonel Rhodes also got a new name. Iron Patriot sounds much more peaceful than War Machine, after all.

28 MICHAEL ROSENBAUM (GUARDIANS OF THE GALAXY VOL. 2)

Michael Rosenbaum Guardians of the Galaxy Vol. 2

If you happen to be a fan of Smallville, you no doubt recognize the name Michael Rosenbaum. In 2013, Rosenbaum’s portrayal of Lex Luthor was included on TV Guide’s list of "The 60 Nastiest Villains of All-Time". And his Lex Luthor was indeed beloved by the fans, despite how much we also hated him at the same time.

Rosenbaum had worked previously with director James Gunn auditioned for the role of Star-Lord in Guardians of the Galaxy, so it’s not surprising that Gunn cast him as Martinex in the sequel.

27 OLIVIA MUNN (IRON MAN 2)

Olivia Munn Iron Man 2

Before Iron Man 2 hit the theaters, the rumors about Olivia Munn’s role were running wild. Predictions were that the actress might be playing an Avenger such as the Wasp or Scarlet Witch. However, Munn was supposed to appear as one of Tony Stark’s many flings, but Jon Favreau scrapped the idea.

Instead, Munn had a cameo appearance as a television reporter Chess Roberts. Though the actress had teased her part in the movie by specifically saying it won’t be a reporter role. While it was a small part, it was a cool cameo.

26 DJ AM (IRON MAN 2)

DJ AM Iron Man 2

Adam Michael Goldstein, known professionally as DJ AM, was an American disc jockey who had a cameo appearance in Iron Man 2. Unfortunately, the musician was passed away in August 2009, before the release of the movie. Released in 2010, Iron Man 2 was dedicated to DJ AM’s memory.

DJ AM appeared as himself deejaying at Tony Stark’s birthday party and provided the soundtrack for the Iron Man vs. War Machine battle. Reportedly, he was only supposed to stay on set for one day, but Robert Downey Jr. took a liking to him, so DJ AM’s stay was extended.

25 TOM MORELLO (IRON MAN)

Tom Morello Iron Man

Tom Morello is best known for his music, rather than acting career. Morello has been a member of both Rage Against the Machine and Audioslave, and he’s currently playing with Prophets of Rage. But the musician does have some acting experience as well.

Those eagle-eyed caught Tom Morello’s cameo appearance in the first Iron Man movie. Morello popped up as one of the members of the notorious organization, Ten Rings. Morello also played the guitar on the soundtrack for Iron Man and Iron Man 2.

24 MILEY CYRUS (GUARDIANS OF THE GALAXY: VOL. 2)

Miley Cyrus Guardians of the Galaxy Vol. 2

You won’t remember seeing Miley Cyrus in Guardians of the Galaxy Vol. 2, but you may have recognized her voice. The former Disney star voiced Mainframe, the artificial intelligence captain of the Ravagers and member of Stakar Ogord’s Team.

James Gunn decided to cast Miley Cyrus after watching her on The Voice. He liked the sound of her voice and Kevin Feige gave him the green light to cast Miley, if Gunn could get her to do it. When Stakar’s Team finally reunited, Mainframe excitedly proclaimed how much she’s missed everyone.

23  JOAN RIVERS (IRON MAN 3)

Joan Rivers delivers Fashion Police advice for Iron Patriot in Iron Man 3 in the MCU

Iron Man 2 is chockfull of television star cameos. Among a number of comedians that appeared as themselves on their respective real-world television programs was the late Joan Rivers. Back when Rivers entered the world of stand-up comedy, there weren’t many women in the business.

Still, the bold and clever Joan Rivers managed not only to claim her seat at the table, but to become one of the best stand-up comedians of all time. In Iron Man 2, Rivers hilariously commented on the subtlety with which War Machine was re-branded as Iron Patriot.

22 SETH GREEN (GUARDIANS OF THE GALAXY)

Seth Green Guardians of the Galaxy

Seth Green is best known as the voice of Chris Griffin from Family Guy and the creator of Adult Swim’s hilarious sketch comedy show Robot Chicken, on which he provides most of the voices. In the Marvel Cinematic Universe, Seth Green made voice cameo appearances in both Guardians of the Galaxy movies.

Green voiced the ill-tempered anthropomorphic Howard the Duck. Unfortunately, it doesn’t seem like Howard the Duck will have a larger role in the future of the MCU.

21 ROB ZOMBIE (GUARDIANS OF THE GALAXY)

Rob Zombie Guardians of the Galaxy

This is one of the oddest cameos in the Marvel Cinematic Universe, so it should come as no surprise that it took place in James Gunn’s crazy space opera, Guardians of the Galaxy. Musician Rob Zombie doesn’t make an actual appearance in the first Guardians film, but you can hear his voice as the Ravager Navigator.

Rob Zombie did appear in Guardians of the Galaxy Vol. 2 as a background Ravager, but he was extremely difficult to spot. Funnily enough, his music wasn’t even referenced once.

20 DANNY PUDI (CAPTAIN AMERICA: THE WINTER SOLDIER)

Danny Pudi Captain America The Winter Soldier

Before they started making movies for Marvel, the Russo Brothers directed a number of episodes of the critically acclaimed sitcom, Community. The sitcom follows a group of characters at a community college, which includes Abed Nadir, portrayed by Danny Pudi.

Pudi can be seen in Russo Brothers’ Marvel debut, Captain America: The Winter Soldier as a communication tech. He didn’t get much screen-time, but he did meet Captain America. Pudi's Community co-star Jim Rash had a cameo in Civil War. Gotta wonder, who's next?

19 LLOYD KAUFMAN (GUARDIANS OF THE GALAXY)

Lloyd Kaufman Guardians of the Galaxy

Guardians of the Galaxy director James Gunn began his career in filmmaking at Troma Entertainment in 1995 when he wrote the independent film, Tromeo and Juliet. Working alongside his mentor Lloyd Kaufman, co-founder of Troma, Gunn learned everything there is to know about making movies.

Once Gunn made it big in Hollywood and got a chance to direct a movie for Marvel Studios he got his former mentor to make a cameo in his film. Lloyd Kaufman played one of the prisoners at Kyln.

18 GARRETT MORRIS (ANT-MAN)

Garrett Morris Ant-Man

Remember that scene in Ant-Man when Scott Lang gets thrown off a building, lands on top of a car and then the camera goes inside of the car to show us this guy? Well, in case you didn’t know already, this is Garrett Morris, a comedian who was part of the original cast of Saturday Night Live.

Fun fact: Morris played Ant-Man in the "Superhero Party" sketch, where Lois and Superman host a party for a bunch of Marvel and DC heroes. The Flash and the Hulk make fun of Ant-Man, and Lois complains to Clark about Superman. It's hilarious.

17 DONALD GLOVER (SPIDER-MAN: HOMECOMING)

Donald Glover Spider-Man Homecoming

When Marvel announced Spidey’s homecoming and a fresh start for the character within the MCU, tons of actors expressed interest in portraying the web-crawler. Donald Glover, who’s best known for Community, Atlanta and his critically acclaimed music video “This is America”, was among those eying the role Spider-Man.

Glover wanted to portray the Miles Morales version of the character, but Marvel went with Peter Parker instead. Still, Glover did get to make a cameo appearance in Spider-Man: Homecoming as Miles Morales’ uncle.

16 NATHAN FILLION (GUARDIANS OF THE GALAXY)

Nathan Fillion Guardians of the Galaxy

James Gunn loves calling up his old friends whenever there's a chance to give them a cool cameo in one of his movies. In 2006, Gunn wrote and directed a horror movie titled Slither that featured alien slugs that infected humans turning them into slug-like monsters. The star of the movie was Nathan Fillion, who had a cameo in Guardians of the Galaxy.

Initial rumors suggested that Fillion could be playing Wonder Man, but that didn't happen (it sort of would later). So, in an homage to one of Gunn's first movies, he had his friend Nathan Fillion voice the slugish blue alien prisoner.

15 JOSS WHEDON (CAPTAIN AMERICA: THE WINTER SOLDIER)

Joss Whedon at the premiere of Avengers: Infinity War

The Russo Brothers managed to squeeze cameos by two different directors into Captain America: The Winter Soldier. Joss Whedon’s cameo is so very discrete that odds are you missed it on your first watch. The Avengers director is seen on the escalator at Smithsonian’s Captain America exhibit.

He’s wearing a Captain America T-shirt, while his son appears to be wearing a Captain America costume. Aside from making a cameo appearance, Whedon also directed the mid-credits scene which introduced Scarlet Witch and Quicksilver.

14 JAMES GUNN (GUARDIANS OF THE GALAXY)

James Gunn Guardians of the Galaxy

James Gunn’s contributions to the MCU, especially Guardians of the Galaxy, cannot be overstated, regardless of how you feel about the recent controversies. Gunn directed two incredible films and gave Guardians of the Galaxy their unique panache. He’s also one of the few MCU directors who acted in their movies.

James Gunn portrayed Maskless Sakaaran, a henchman of Ronan the Accuser, in the first Guardians of the Galaxy movie. Plus, he provided on-set dance moves for Baby Groot’s dance number in Guardians of the Galaxy Vol. 2.

13 JOE RUSSO (CAPTAIN AMERICA MOVIES)

Joe Russo Captain America The Winter Soldier

One half of the Russo Brothers duo, Joe Russo seems to be fond of cameos. So far, Joe Russo has made two cameo appearances in the MCU, credited as Gozie Agbo. In Captain America: The Winter Soldier, Joe Russo appears as the doctor who operated on Nick Fury.

In Captain America: Civil War, Joe Russo played a different doctor. Doctor Broussard was hired by to interrogate Bucky Barnes -- a task he couldn’t complete because he was killed by Helmut Zemo.

12 J. MICHAEL STRACZYNSKI (THOR)

Thor J. Michael Straczynski

J. Michael Straczynski is known for his run on The Amazing Spider-Man from 2001 to 2007, but he’s also worked on several other Marvel titles, including Thor. You might also recognize him as one of the co-creators of Netflix’s Sense8, as well as the writer of Before Watchmen: Dr. Manhattan and Nite Owl.

Straczynski is one of two Thor writers to make a cameo in the first Thor movie. Straczynski appeared as the truck driver who unsuccessfully attempted to pull Thor’s hammer out of the ground.

11 WALT SIMONSON (THOR)

Walter Simonson smiles at a comic convention

Comic book writer and artist Walt Simonson is best known for his run on Marvel Comics’ Thor from 1983 to 1987. During that time, Simonson created the now-beloved Beta Ray Bill. Though, the Korbinite deemed worthy to wield Thor's hammer hasn’t made an appearance in the MCU yet, his face did appear on the Grandmaster’s monument at Sakaar.

Beta Ray Bill’s creator Walt Simonson made a cameo in the first Thor movie. Simonson is briefly seen sitting beside Lady Sif during the festive dinner on Asgard.