In sooper appisote 3, the entire series’ font gets changed midway through the sooper appisote, due to someone pressing a button that said “CHANGE FONT”.
And in A.18, Liteslayer and Deine indirectly break the fourth wall by acknowledging the live “evolution” happening to them. It starts by a text-to-speech-translator, getting colored, then spelling properly, then so on and so forth until Lite kills himself to stop any more “evolution” from happening.
KateModern comes dangerously close to breaking the fourth wall on a number of occasions, always with some in-universe justification (however flimsy). They finally break it directly in "The Last Work", when Tez, after talking to an off-screen Meryl, turns to the camera and says, "She should get her own show, that one." This was also a direct Shout-Out to the fanbase, as the concept of a Spin-Off called "MerylModern" was a popular fan in-joke.
Certain characters in Star Harbor Nights are "meta-aware", notably the Hex Kittens and the inhabitants of the Sands of Time, the local Inn Between the Worlds. Most often used for Lampshade Hanging.
The chapter Super VisionLampshades this when Johnny Dark cautions Maria not to overthink the nature of the Sands, because it makes the author irritable. Later, Tigerlily Bender seems to fall afoul of this same phenomenon.
Many an abridged series will do this on a regular basis. To the point that Ishizu mentions she can break the fourth wall in her first appearance, and this is unimpressive because everyone else has already broken it.
This is an actual plot point in Yu-Gi-Oh! The Abridged Series. According to Ishizu, if the fourth wall collapses completely, then Yu-Gi-Oh Abridged will be cancelled. Sure enough, Melvin defeating Florence is enough to bring the fourth wall down (for some reason), and 4kids (as run by Noah and the Big Five) cancel the show... And then LittleKuriboh announces Season 3. Yeah. Trippy, much?
And now we have season 3. First off Serenity tries to talk to Joey about the fact that she's frightened she'll get written out of the show because her character doesn't serve any significant point... And then all the main characters are told their show has been cancelled. Their reaction? "What the fuck?!" Just... There's no fourth wall any more. There's a fifth wall, but the fourth wall is just broken. And no, it is not going to be revived from the shadow realm.
In Avatar: The Abridged Series, Iroh actually teaches Zuko how to break the Fourth Wall. He ends up using it to re-write the episode to make Sokka's life hell.
Bioshock Above The Sea: Zero does this twice, once, when a roleplayer states her upset at being dumped Zero "kills" her ex in the actual roleplay, and another time when he spends a few seconds speaking with the roleplayer that made him.
This was a prominent running gag in "We Are Our Avatars", where characters like Bass, Deadpool, Bernkastel, "Raven", among others, would refer to the readers and the people reading, but, the gag was done to death and it's since been downplayed. It got to the point where Etheru retconned the ability out of Bass because of annoyance with the gag.
In The Guild, Codex breaks the fourth wall at the start of every episode, talking to the audience about what's bothering her.
In the Whateley Universe, the Monkey King is a godlike being who apparently has this as a power. In his own point of view short story, he repeatedly addresses the readers and even makes comments about some of the forum posters.
In one of the Soul Pancake video "Unexpected Visitor" the intruder tells the guy, and atheist he is God, the guy says "you just lost me" to which God says "that's okay, we probably just lost about Half our audience." then looks and winks at the camera.
There is a bit of fourth wall breaking in The Cartoon Man saga. While no one ever acknowledges their existence as characters in a movie, Roy looks into the camera numerous times as if acknowledging an audience. It's played as one more aspect of acting like a cartoon character. Roy and Valerie also go through a "montage" in the third movie, and specifically refer to it as such.
In Ask King Sombra: Being that it's an ask blog, naturally, the characters respond to fan comments. It's a bit zigzaggy on whether other characters realize that that's what they're doing though.
Sombra is actually able to physically interact with the question boxes; at one point he tries to hide behind them, only to realize they aren't actually real.
At one point the author tries to derail the comic into a shipping fic, so Sombra and Coffee Talk open a portal and give his Author Avatar a Death Glare to make him get back on track.