Born in the Theatre

Prior to the advent of TV, cartoons were produced for theatrical release only. They were either run as shorts before the showing of the feature film, or shown on a weekend matinee.

As a result, there are a few No Fourth Wall jokes that appear in 1930s and 1940s vintage cartoons that would make absolutely no sense to a modern audience watching it on television or unaware of the history.

Nowadays, you'll mainly see them in Looney Tunes shorts.

Most common include:
 * A character runs full tilt towards the edge of the screen, the camera follows him, and pans beyond the film itself into the blank white nothingness of an empty theater screen. The character realizes what has happened, and jumps back onto the film.
 * The hero is trapped, there's no possible escape, and just as it looks like he's about to get it, the film breaks. Cue blank white screen. The hero appears and explains that due to technical difficulties, the film cannot be finished, and may produce a pair of scissors and hint that it wasn't exactly an accident.
 * A black silhouette of a person scrolls across the bottom of the shot; the characters admonish the theater patron to "sit back down!"
 * An apparent hair caught on the film flutters around for a bit before the character on screen stops what he's doing, picks it up, and discards it.
 * Occasionally asking "Is there a doctor in the house?" in combination with Amusing Injuries.
 * House being a term for "theater".
 * The animation suddenly becomes partially inverted (swapping the top 50% of the image with the bottom 50%), jerky, and even shows the rows of pinholes on the sides, imitating a film jam or other problem with the theatrical projection camera. In extreme cases, the jammed film appears to melt and burn from the heat of the projector bulb.

Anime

 * The Osamu Tezuka short Broken-Down Film is full of these type of gags, seeing as it is presented as a bad print of a silent-era cartoon set in the Old West. The characters are constantly reacting with the deteriorating film stock - wiping away the surface dust, for example, or escaping the villain while the film is misaligned.
 * Tenchi Masaki's near-death out-of-body experience in the 19th Tenchi Muyo! OVA episode was represented as the classic clattering of a malfunctioning projector and film sliding out of position. Never mind that it was made in the 21st century on computers for a DVD release.

Film

 * In the movie Fight Club, the pointing out of a Cue mark (called, inaccurately, a Cigarette burn). The movie also used a fake subliminal movie frame at the end.
 * Not just the end. Tyler Durden appears at least five times in flickers of frames before he's introduced.
 * Scrooged ends with a CMOA that invokes this trope, when Frank Cross breaks the fourth wall to address the theatrical audience directly, even asking them to sing along to the closing credits -- first the people on the right, then the people on the left...
 * Groucho Marx talked to the audience a lot (most likely carried over from the brothers' vaudeville days) - in Horsefeathers, as Chico starts a piano routine, Groucho looks at us and says "I've gotta stay here but there's no reason you folks shouldn't go to the lobby 'til this blows over!"
 * In the theatrical version of Gremlins 2, there comes a point where there seems to be a problem with the projector and the film breaks, leaving a blank white screen. It turns out to be gremlins in the projection booth, who wickedly decide to replace the film with a naturism film, and an usher calls upon Hulk Hogan to restore order. Later VHS and DVD releases replace this with a gag appropriate to home video viewing.
 * Even the novelization of the film has a gag sequence where the "Brain" Gremlin (the one who can talk, voiced by Tony Randall in the film) locks the author of the novelization in another room while he types up his own contribution.
 * If you go to YouTube there's a whole slew of homemade ones that fans cooked up including one where the title creatures make the mistake of of screwing around with The Goddamn Batman.
 * A trailer for Pink Panther 2 running in theaters in August 2008 showed Steve Martin as Inspector Clouseau sneaking into a movie theater; after the screen switches to a generic "please turn off cell phones and pagers" display, there is a ripping sound and Clouseau appears to cut a hole in the movie screen and step through. Upon discovering the audience watching him, though, he sheepishly steps back through the hole and ineptly tries to repair it with duct tape. The screen then becomes "rear illuminated" to show the movie logo and to highlight the silhouette of Clouseau tiptoeing behind it... followed by the silhouette of the Pink Panther himself.
 * At the end of The Thief and the Cobbler, the thief removes the film from the projector and absconds with it. Talk about a scene stealer!
 * Kiss Kiss Bang Bang's Lemony Narrator will regularly pause, rewind, or write on the film itself -- in addition to making commentary on it -- to make certain points.
 * The melting film gag is used on Monsters vs. Aliens to transition from the black-and-white (and, on the 3-D version, flat) version of the Dreamworks Animation logo and into the film proper.
 * At the end of Despicable Me some of the minions try to reach into the audience. One flies right into the camera, the film breaks and suddenly he's silhouetted against a blank screen, the implication being that he's flown right into the projection room.

Live Action TV

 * In an animated link in episode 28 of Monty Python's Flying Circus, a skeleton steps out of a medical poster and walks off. Ignoring warning signs and voices, it wanders so far as to fall off the edge of the film.

Western Animation

 * The old Tex Avery short "Lucky Ducky" had a pair of hunters chasing a duckling. In mid chase, the film suddenly turns from color to black and white. The characters stop and notice they have run past a tiny sign that says "Technicolor ends here". Technicolor is the name of the company that developed colored movie camera film and perfected it for use in the early 1930s.
 * In another Tex short, "Billy Boy", a farmer is trying to rid himself of a goat who's eating everything he owns. One attempt to dispose of him fails when the goat eats the half of the screen the farmer was standing on.
 * Yet another Avery short, Magical Maestro, included an animated 'hair' caught in the projector gate that was so realistic it drove projectionists crazy...until the action suddenly stops and one of the characters plucks it and throws it away.
 * Woody Woodpecker has pulled this once or twice. For example, in Who's Cookin Who?, when Woody is starving, he asks "Could somebody go to the lobby and get me a candy bar?"
 * Also pulled in the short The Screwdriver, in which Woody is quizzing a cop, and reminds us "No coaching from the audience, please!"
 * In Yellow Submarine, leaving Nowhere Land involved crossing a film sprocket line. (Unless that got remastered out...)
 * The Bugs Bunny cartoon Hare Tonic has Bugs convincing Elmer that he has "the dreaded disease rabbititis." When Elmer catches on and chases Bugs out of the house, Bugs tells him that the audience is coming down with rabbititis. As Elmer runs back inside, Bugs reassures the audience that they're just fine, because if they were sick, they would see red and yellow spots before their eyes, and they would start swirling around until everything went dark. Sure enough, red and yellow spots appear on the screen and swirl around until the screen fades to black... after which we hear Bugs snickering. This is actually extremely common in the Merrie Melodies/Looney Tunes short. See also:
 * "The Ducksters", featuring Daffy as a sadistic game show host; he shoots a member of the 'audience' for warning Porky. Also- "Have you got a doctor in the balcony, lady?!"
 * In the Porky Pig cartoon "The Case of the Stuttering Pig", the villain was defeated when he got clocked with a flying theater seat courtesy of "the guy in the third row", whom he'd earlier derided as a softy.
 * In "Rabbit Every Monday" Yosemite Sam threatens a silhouetted person with his gun and tells him to sit back down, which the person does while yelping a meek "Yes Sir!" He then turns to the audience and declares "That goes for the rest a' ya!"
 * The Bugs Bunny cartoon Rabbit Punch ends with Bugs Bunny about to be run over by a train. As the train barrels toward Bugs, the film breaks. Bugs walks onto a blank screen and announces, "Ladies and gentlemen, due to circumstances beyond our control, we are unable to finish this picture. And, uh, confidentially," he adds, holding up a pair of scissors, "the film didn't exactly break."
 * Similar ending to the Daffy Duck cartoon My Favorite Duck, where the film breaks while Porky Pig is chasing Daffy Duck with a gun. Daffy then appears and offers to finish the cartoon as a narrative and gives a brief and inflated description of him beating Porky with his bare hands leaving him "groveling at my feet!" Only to have Porky sneak up behind him and club him over the head to end the cartoon.
 * In the short Daffy Duck and Egghead, after several silhouette interruptions, the annoyed character on screen shoots the patron who falls dead.
 * In Duck Amuck, the film appears to slip in the projector, resulting in a top-bottom frame reversal. The two Daffy's from each frame then start arguing with each other: "If you wasn't me, I'd smack you right in the puss!"
 * The best "doctor in the house" moment came in "Hair-Raising Hare": chased by a monster, Bugs Bunny runs through a door, slams it shut, leans up against it panting and begs of the audience, "Is there a doctor in the house?" A silhouette stands up and raises a hand: "I'm a doctor." Bugs pushes off from the door, pulls out a carrot, and gives his Catch Phrase: "Eh, what's up, doc?"
 * "Look, out there in the audience..." "PEOPLE! AAAAAAAAAH!" In that same cartoon, Bugs Bunny disposed of Gossamer the big orange monster by frightening him into running out through the back wall of the theater, and through numerous other walls behind it, leaving behind a tunnel of Efficient Displacement.
 * In the Bugs Bunny cartoon "High-Diving Hare", Yosemite Sam is pounding on a door shouting "Open the door!" - he then turns to us and says "Ya notice I didn't say 'Richard'!" before resuming pounding. "Open the Door, Richard" was an old vaudeville routine (later a popular song).
 * While not actually produced for theaters (it's a TV show, after all), at least three gags in Tiny Toon Adventures invoked it. One of these occurrences had Hamton J. Pig joyriding in the Batmobile, and upon making a big swerve to dodge a building, he briefly flies out of the film strip. Another episode had Hamton threatening an anthropomorphic fire, and the camera pans out to reveal that the scene is being played out on a film strip. The fire proceeds to burn the strip, comically reducing Hamton into a roasted pig. The Whole-Plot Reference Christmas special had Buster at the edge of a film reel, contemplating suicide ala George Bailey. He later does jump out... in joy, and lands right back in the "film" (this is after he is granted a second chance at life).
 * There's also the one with Plucky and Hampton breaking into Warner Bros. Studio through the sewers (Or was it busting out of jail? Either way...) with a Teenage Mutant Ninja Turtles reference. This being the nineties, everyone in the "audience" is vocal about having seen that one coming.
 * During The Emperors New Groove, the film stops and Kuzco appears to point out that the story is about him, not Pacha, even drawing on the film frame with a marker to make his point. Interestingly, this gag is reused on The Series.
 * In Kronks New Groove, Kuzco again interrupts to point out that this one is about Kronk and not him, actually bringing out the films' posters.
 * In the Popeye cartoon How Green is My Spinach, a Dangerously Genre Savvy Bluto creates a formula that wipes out all the spinach in the world, including Popeye's. As Bluto sweeps the floor with Popeye (literally), the narrator asks, "Can this be the end of our hero? Can't anybody save him? Is there a can of spinach in the house?!" The short abruptly goes from a color cartoon to black & white live-action, showing people watching the cartoon (still in color) in a movie theater. A worried boy pulls out a can of spinach from a grocery bag, yells, "Here, Popeye, catch!", and tosses it to the screen. You can probably guess the rest.
 * The Popeye cartoon Goonland climaxes with Popeye and his Pappy fighting dozens of Goons - the violent action ends up snapping the film itself, and the Goons plummet off the screen. As the audience stomps and whistles, a realistic pair of hands mend the film and it resumes with our heroes saved.
 * A third Popeye example: In the cartoon The Hungry Goat, Popeye's commanding officer leaves for a day at the movie theater, and warns him not to harm the goat. Later, as Popeye is about to throttle the goat for eating the boat, the goat warns that the admiral could be watching them right now -- and sure enough, he is seen silhouetted against the screen, taking his seat. At the end of the cartoon, the admiral sees the damaged being done to his ship and runs back. He asks Popeye where the goat went, and we see the goat sitting with the audience, laughing.
 * And more Popeye. In A Date to Skate, Olive Oyl is careening out of control on a pair of roller skates and Popeye reaches into his shirt for his Spinach can...only to find it missing. After patting himself down for a few seconds and declaring, "Now don't tell me I left it at home!", he finally shouts, "Is there any spinach in the audience?" A shadow of an audience member emerges from the bottom of the screen, lobbing a spinach can toward Popeye who catches it, eats, and goes to rescue Olive.
 * The Simpsons do it at least twice (could be more):
 * in one of the opening sequences the whole family runs off the film;
 * in The Movie, Homer addresses (and insults) the audience.
 * At least twice, Foghorn Leghorn stretched out the closing iris that ended the cartoon because he wasn't finished talking. This gradually stopped as his gimmick became playing practical jokes instead of being a Motor Mouth.
 * This joke has since been inherited, and used at least twice, by Pinkie Pie.
 * Speedy Gonzales runs past a cat, and the cat then explodes. Speedy then turns to the audience, apologizes for running too fast for the audience to follow and shows the previous scene again in slow motion. The slow motion shot involves Speedy pulling another mouse out of the cat's mouth, and replacing the mouse with a lit stick of TNT.
 * Who Killed Who includes one of these gags just as the cop enters the house. After he warns "Nobody move!", a silhouetted audience member gets up and shuffles across the bottom of the screen. The cop sees him and bashes the poor guy with his nightstick, before shouting "That goes for you too, bub!".
 * In "King Size Canary" a mouse warns a cat not to eat him because he'll save his life later on. He knows because he's already seen the cartoon before!
 * The side effects of the Virus from the Strong Bad Email "virus" from Homestar Runner, particularly the scene where Strong Bad accidentally leaps off the screen and cannot jump back in, and at the same time, Homestar Runner (whom, as a result of him being affected by the Virus, has The Homestar Runner's torso) detaching his own head and using it to pick up certain icons on the navbar on the bottom of the screen.
 * Then several windows resembling pop-up windows show up on the screen, one of them being an actual pop-up browser window, which Firefox will often block.
 * The framing device from The Lion King 1 1/2. "Pumbaa! You sat on the remote!"
 * At the end of Aladdin, the Genie actually lifts up the film and says, "Made you look!".