The "fourth wall" is the invisible barrier between the fictional world and the real world, the thing that separates the characters in a comic from the people reading the comic. The term comes from stage plays, where every room has only three walls, because the fourth wall is the one we look through to watch the show. The actors in the play always ignored the fourth wall, unless they were talking to the audience.

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Just like in the old plays, sometimes a superhero or supervillain really will break through the page to address us, the readers, and it's always a shock, but also awesome. Some characters are known to do it once or twice, while others do it all the time. Here are 16 comic book characters who've broken that fourth wall, and why they did it.

16 JACK OF FABLES

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"Jack of Fables" (written in 2006 by Bill Willingham and Lilah Sturges, art by Tony Akins, Andrey Pepoy, James Jean and Brian Bolland) was a spinoff from the original series "Fables," about a world where the characters from fairy tales lived among humans. Jack Horner was one of the most powerful of the fables, because he starred in a hit movie trilogy he made about himself. However, since he broke the rules of the community, he was kicked out of Fabletown to be forgotten.

Jack knew he was a comic book character, and would talk to the reader in narration. He even lied in the teasers about what would happen in the next book. At one point, he met Eliza Wall, the literal personification of the Fourth Wall, who talked right at us, the readers. Unfortunately, Jack insulted the artist, who punished him by causing him to gain weight, lose his memory and become a dragon to be slayed by his own son, Jack Frost. Never mess with the artist.

15 CEREBUS

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Beginning in 1977 and ending in 2007, "Cerebus the Aardvark" was one of the longest-running works of comic book storytelling in Western history. Written and drawn entirely by Dave Sims, "Cerebus" ran over 6,000 pages, starting as a comedic satire about an aardvark journeying through a fantasy world (sort of like "Teenage Mutant Ninja Turtles" crossed with "Conan: The Barbarian") and ended as a serious dramatic work. It also broke the fourth wall in a big way.

In the story arc "Minds," Cerebus was traveling through space, seeing moments from his past, and begging his god to save him. In issue #193, he began hearing a voice in his head calling itself "Dave," the voice of Dave Sims, his own creator. Dave spoke to him, giving him advice and showing Cerebus alternate futures to help him decide his fate. It was a trippy and surreal break in the fourth wall, but it was just the beginning when it comes to our next entry.

14 BAT-MITE

Bat-Mite holds a Golden Age DC comic book

If God was a nerd, he would be Bat-Mite. Bat-Mite is to Batman as Mister Mxyzptlk is to Superman, a god-like imp who seems able to do anything, but lives to torment the hero. Bat-Mite first appeared in 1959's "Detective Comics" #267, by Bill Finger and Sheldon Moldoff. He disappeared in 1985's "Crisis on Infinite Earths," but was brought back by popular demand to the post-Crisis universe.

Wearing a goofy-looking Batman costume, Bat-Mite idolizes his hero and uses his powers to put Batman into fun situations so he can watch. Basically, he's like a nerd who goes "Could Batman beat Superman? Let's find out." Bat-Mite is fully aware of his existence as a comic character, and visited DC comics in one story to get his own feature. In four episodes of the TV show "Batman: Brave and the Bold," Bat-Mite referenced and made fun of comic conventions of the time. He's the ultimate fan, only smaller.

13 SCOTT PILGRIM

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In 2004, Bryan Lee O'Malley began a series of graphic novels called "Scott Pilgrim" about a slacker and Canadian musician who has to go through a series of battles against the ex-lovers of Ramona Flowers in order to win his true love and be able to date her. The comics referenced all sorts of material beloved by geeks such as manga comics, video games, underground music and American comic books. Since he's on this list, it should go without saying that Scott Pilgrim also knew he was inside a comic book.

It wasn't an open thing like talking directly to the readers, but he would often talk about the comic itself. When Ramona asked Scott about his job, he said he would explain it in "Volume 3." While fighting Ramona's vegan boyfriend Todd, Scott wished for a "deux ex machina" right before one appeared in the form of the Vegan Police. He wasn't the only one, like when another character interrupted the comic to give a recipe for vegan shepherd's pie. It should have been called "Scott Pilgrim vs. the Fourth Wall."

12 SUPERBOY-PRIME

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Superboy-Prime is from a world of superheroes, but rather than land on that Earth, he was sent from that universe's Krypton to the universe known as Earth-Prime, a world where DC superheroes and supervillains only exist in comic books (it's basically a pure copy of our real-life Earth). He first appeared in 1985's "DC Comics Presents" #87 (by Elliot S! Maggin and Curt Swan), a variation of the original Superboy by Jerry Siegel and Joe Shuster. He was taken to the DC universe during 1985's "Crisis on Infinite Earths," but when the DC multiverse collapsed, Superboy-Prime left to a "paradise dimension." He didn't stay there forever, though.

In 2005's "Infinite Crisis," Superboy-Prime grew so angry that he punched reality itself, causing ripples of change in the DC Universe, and eventually smashing his way through and back into the mainstream dimension. When he tried to make himself the only Superman, Superboy-Prime failed and was sent back to Earth-Prime. There, he began reading DC comics and trolling the message boards, talking directly to the reader, and even attacking DC comics headquarters. He's DC's worst nightmare: a super-powered Internet troll.

11 RICK JONES

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When it comes to the Hulk, Rick Jones was there from the beginning. He first appeared in "Hulk" #1 in 1962, created by Stan Lee and Jack Kirby. He was just a teenager who went out on an open military field on a dare, not knowing the field was going to be a testing ground for a new gamma bomb. When Dr. Bruce Banner tried to save him, he was caught in the explosion, turning Banner into the Hulk. From then on, Jones became Banner's sidekick, and also became the sidekick to other heroes like Captain America.

Jones has always been a comic book geek who referenced the other characters and their adventures, but his fourth wall moment came in the final issue of 2004's "Captain Marvel" #25 (Peter David, Keith Giffen) where the cosmic entity Eulogy comes in to explain their adventures are ending and takes away the world. Only Jones really understands that the comic is being cancelled, thanks to his "comics awareness."

10 SQUIRREL GIRL'S SQUIRRELS

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Everybody loves the unbeatable Squirrel Girl, but nobody can beat her. Squirrel Girl was created by Will Murray and Steve Ditko in 1992's "Marvel Super-Heroes" #8, where she was just a girl with squirrel powers (claws, strength, the power to command squirrels) geeking out over meeting Iron Man. She somehow managed to defeat Doctor Doom, Thanos and Wolverine without resorting to gimmicks like Doombots or imaginary stories.

In 2015, "Unbeatable Squirrel Girl" became her own series by Ryan North and Erica Henderson, and each issue starts with a recap by her. Each page also has footnotes from her that reference the comic book you're reading. In the actual story, Squirrel Girl herself tends to stay in the comic book world, but her sidekick squirrels Tippy-Toe and Monkey Joe break through the fourth wall to comment on and critique the art and story. Sometimes, they'll even tease the readers for taking things too seriously, as seen in the image above.

9 ALEXANDER LUTHOR JR.

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We mentioned Superboy-Prime earlier, but he didn't go to the "paradise dimension" by himself. He also left with Alexander Luthor Jr., who first appeared in "Crisis on Infinite Earths" #1 (Marv Wolfman, George Pérez, Jerry Ordway) as the son of an alternate Lex Luthor who's a hero and married to Lois Lane. Alexander Luthor became frustrated by the "paradise dimension" as well and escaped into the mainstream DC universe to take Lex Luthor's place and create a perfect world - at least, perfect from his perspective.

"Infinite Crisis" was really a commentary on the comic industry with Alexander and Superboy-Prime angry at the dark and gritty turn that comic books had taken, and wanting to return to the lighter stories of the Silver Age. In one moment, Alexander is looking for alternate worlds to combine into a single Earth. While searching for a perfect world, he looks straight at the reader and seems to reach out to grab us. Fortunately, he's stopped. That's why we're still here.

8 MISTER MXYZPTLK

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Like Bat-Mite, Mister Mxyzptlk is a trickster from the fifth dimension with almost limitless power who can change reality to become whatever he wants. Unfortunately, he's not as nice as Bat-Mite, choosing to torment and torture Superman and other heroes. With his interdimensional travel beyond the known DC universe, it's not much of a stretch. After all, he broke through the third dimension. Why not the fourth wall?

While lots of Mxyzptlk's adventures have been meta, his most wall-breaking-est moment came in 2001's "World's Funnest" (written by Evan Dorkin and drawn by 19 artists including Frank Miller, Frank Cho and Dave Gibbons) where Mxyzptlk and Bat-Mite got into a battle that destroyed multiple universes. In the process, Mxyzptlk used a giant eraser to wipe out Captain Carrot's universe and tore up the page in another universe. At one point, the two imps even crossed over into photos of the "real world" in New York City.

7 JOKER

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Since his first appearance in 1940's "Batman" #1 (Bill Finger, Bob Kane and Jerry Robinson), the Joker has been bringing chaos and destruction to the DC universe in general, and to Batman directly in particular. Whenever he's not killing people in Gotham City, he's usually hanging out at Arkham Asylum, where they try (unsuccessfully) to treat his insanity. He might not actually be as crazy as he seems, since he seems to know he's in a comic.

At one point in "Detective Comics" #476 (Marshall Rogers, Steve Englehart), the Joker spent a page talking about his plan to no one (unless you count us, the readers) then reached out and turned the corner of the page. In 2010's "Batman 80-Page Giant," Joker had an argument with a psychiatrist about why he does what he does for his fans, because he's believes he and the psychiatrist are fictional characters. He ends by asking if his fans are real, looking right at the reader. Creepy.

6 SUPERMAN

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Of all the superheroes in the DC universe, Superman seems to be the most powerful. First appearing in 1938's "Action Comics" #1 (Joel Siegel, Joe Shuster), Superman is the alien from Krypton with powers far beyond mortal men. He can fly, is super-strong, has X-ray vision and heat vision, among other powers. His vision also seems to let him see through the page, because he apparently can see through the fourth wall.

In his appearances during the Silver Age, Superman seemed way more casual about the fourth wall. At the end of the story, when Clark Kent would make a joke about his secret identity, he would often turn and wink at the reader. No doubt Lois Lane would look at him and say, "Who are you winking at?" Kent would go, "Oh, no one," and then wink again. After a while, his friends probably stopped asking and would be like, "Just let it go, man."

5 ULTRA COMICS

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In 2015, Grant Morrison and Doug Mahnke created "Ultra Comics," a one-shot about a world without superpowers that created an all-powerful being made of paper and ink, literally a comic book made into the superhero named Ultra Comics. Powered by the collective consciousness of the book's readers, Ultra Comics set out into the comic book world to save a post-apocalyptic world and find the reason for his creation.

The point is that "Ultra Comics" was allegedly alive and happening in real-time. The book started with the superhero beaten up and looking directly at you, saying he was from "38 pages in your future," warning you not to read the story. The readers' minds gave Ultra Comics his power, and he spoke to you and reacted as you turned pages. The comic built on all the stereotypes of superheroes, then veered sharply into a bizarre post-apocalyptic world involving cannibals and an attack on your own brain.

4 AMBUSH BUG

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Created as a comic foil for Superman by Keith Giffen in "DC Comics Presents" #52 in 1982, Ambush Bug is a mysterious man wearing a green bodysuit with long antenna whose only powers are teleportation and dumb luck. He went from a bad supervillain to a bad superhero, trying to fight crime with his stuffed toy "Cheeks the Toy Wonder." He's insane, if you haven't guessed.

It may be the insanity that gives him the power to break the fourth wall, but he's completely self-aware. He constantly argues with his creator and editors during the course of his stories. He'll jump through panels and word balloons, change the story when he doesn't like where it's going, and was even taken to court by DC comics for "contempt of comics." He's currently a field reporter for "Channel 52," backing up several books with commentary on the state of the DC universe.

3 SHE-HULK

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She-Hulk first appeared in "Savage She-Hulk" #1 (created by Stan Lee and John Buscema) in 1980. When Jennifer Walters was critically injured, her cousin Bruce Banner gave her a blood transfusion. The result of receiving his gamma-irradiated blood was that she developed the power to transform into the super-strong jade giant known as She-Hulk. She-Hulk became a popular comic book hero, serving as a member of the Avengers, Fantastic Four and many other superhero teams.

She wasn't aware of her persona as a comic book character until 1989, when John Byrne started her solo title "The Sensational She-Hulk," in which she began to break the fourth wall, demanding that people read her book. Throughout her series, She-Hulk would have arguments with Byrne and the book's editor, and even fired her own narrator. In one story, she ripped through the page to travel through an advertisement. She's a mean, green, fourth-wall-ripping machine.

2 ANIMAL MAN

Animal Man meets his writer, Grant Morrison, in DC Comics

Most of the time when a character breaks the fourth wall, it's played for laughs, but Animal Man was dead serious and even tragic. When Animal Man (first called A-Man) appeared in 1965's "Strange Adventures" #180 (Dave Wood and Carmine Infantino), he was never popular. With the ability to adopt animal powers, he made appearances in just 11 stories over 20 years before the "Crisis on Infinite Earths."

All that changed in 1988 when Grant Morrison wrote the new "Animal Man" series which gathered critical acclaim. After the death of his family, Animal Man was drawn into Arkham Asylum, where the Psycho-Pirate tried to release characters erased by the Crisis back into the DC universe. To stop him, Animal Man journeyed through Limbo, the world of unused characters, into a black-and-white version of the "real world." There, he had a metaphysical conversation with Morrison himself about why he had been put through so much grief. It was a sober discussion about the nature of storytelling and violence.

1 DEADPOOL

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They call him the merc with the mouth for a reason; it's because he can't stop talking, usually about his own fictional nature. Yeah, we're talking about the deadly and always wisecracking antihero Deadpool here. First created by Rob Liefeld and Fabian Nicieza in 1991's "The New Mutants" #98, Wade Wilson started out as a supervillain who was so popular that he became a hero. He recently became a global sensation with his hit movie, bringing his fourth wall-breaking with him.

One of the running jokes with "Deadpool" comics is that he's fully aware that he's a comic book character. He often breaks the fourth wall to comment on his own comic and the reader, referencing previous issues and his own narration in "little yellow boxes." In "Deadpool Teamup" #885 (Rick Spears, Phil Bond), he even cut open his own page to yell something to himself earlier in the issue. He doesn't take anything seriously, and that includes his own comic book.

Who is your favorite fourth-wall breaker? Do you love or hate when it happens? Let us know in the comments!