A Painting the Fourth Wall and Medium Awareness trope, where characters interact with the confines of the scene. For example, interacting with borders around comic strip panels by crashing through the side or falling out the bottom. In live action media, it might be that it is implied that two characters are in a different settings, in different buildings, yet one of them can reach into the other setting.
A Sub Trope of Odd-Shaped Panel and Ninja Prop.
Examples
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Anime & Manga
Dragon Ball: Once, Goku is hit so hard he bounces off the edge of the panel.
Obligatory Mahou Sensei Negima! example: Negi, Blue with Shock, holds on to the frame in a "Kilroy was here" pose when he contemplates what Evangeline's going to do to him for losing the ring she gave him.
When a character is formally introduced in One Piece, they often stand outside the panel, overlapping it.
Comic Books
She-Hulk did it once or twice in her Genre Savvy days. One issue of She-Hulk has her ripping through two pages of ads to go after a villain.
Ambush Bug once jumped back several pages to rescue Cheeks.
A recent issue of Superboy had Doomsday actually a clone of him smash through the entire bottom half of a page in attacking Superboy, destroying the frames in the process.
Has been used in The Beano a number of times and in the Beano Video as well.
Pearls Before Swine does this several times, as well as "Panel Walking" between comics.
Pearls once had a joke that relied on proper placement in the paper. One day, Family Circus had Billy denying that he was spilling sunflower seeds in the kitchen. The Pearls strip that day had Rat throwing sunflower seeds down and out of the panel. When positioned directly above Family Circus, Rat's abuse of the long-running comic became apparent.
Every so often a character in Pogo would literally lean on the fourth wall this way (or at least against the frame border); on occasion Albert would use it to strike a match for his trademark cigars.
Little Nemo In Slumberland used this on occasion. In one strip, Flip tears off the bottom frame of a panel and uses it to knock down letters from the comic's logo.
Video Games
Comix Zone makes use of this trope, as it takes place in a comic book. Not a comic book world, the actual pages.
The Order of the Stick plays with this sometimes. Haley gets knocked into the next strip in the fight with Tsukiko. (The strip in question is called "At Least It Wasn't the Fourth Wall This Time.")
Haley also climbs up the 'panes' of the cast page to borrow a diamond from herself.
Here, a massive fire spreads beyond the panel borders, and even onto the following page (an effect that will presumably be more impressive in the print version).
We see a similar trick in "Free," where a stickman tries to dig his way out of the frame.
The Way of the Metagamer does this. A lot. Looking at previous and future panels, climbing between panels, and even pulling a section out of a panel are common occurrences.
In Unbound, events sometimes spill over the sides of the comic. In one case a fire spreads to the 'paper' of the website's background, leaving it blackened once the fire is out.
In Unsounded, weird supernatural stuff—like certain fires, or metaphorical snake skeletons—extend off the page. When the characters walk through a dark tomb, the entire webpage is darkened.
Bob and George. During the Mega Man 5 parody, the protagonists split up and the comic began running two strips per day so the plots for both groups could update concurrently. After about a month of these updates, the characters in the bottom strip began wondering how their allies were doing, so they climbed into the strip above them to ask.
In Mixed Myth, Tamit learns the secret of Time Travel, and it involves seeing the comic panels. She then demonstrates her mastery by reaching through time (i.e. across the panel borders) to poke someone in an adjacent panel.
In thisOut at Home strip, Penny bats a speech balloon from one frame to another.
Gavin, the main villain of The Fancy Adventures of Jack Cannon, here tries to trap the titular hero in a shrinking panel frame, and Jack has to break it to escape.
Western Animation
In The Fairly OddParents, when Timmy magically goes into the Crimson Chin comic book, he's able to jump from frame to frame (and time travel by doing so).
In the intro of The Beano Video we see numerous instances of this including Teacher being used by the Bash Street Kids as a battering ram.
