Breaking the Fourth Wall

Breaking the fourth wall is a term that essentially means characters in fiction implying or demonstrating that they're aware that they're fictional. For instance, they might look at the camera, talk to the audience, or mention something out-of-universe.

The term comes from theatre and refers to how a stage has three walls, and actors generally imagine a fourth one between themselves and the audience so that they can be in-character, but if a character implies that they know they're fictional, this wall is "broken".

Times the Fourth Wall was Broken in The Petri Dish

 * In a strip during Irene's debut, Bob imagines EVE from the Pixar movie WALL-E, but Thaddeus Euphemism tells him, "No graphic thought bubbles! You want me to get sued?!!" (even though, if Bob's thought bubble did result in a lawsuit, it'd be the creator John Sutton being sued, not Thaddeus).
 * The comic's 200th strip has Bob be aware that he and Thaddeus are in a comic and demand Thaddeus celebrate it. iBall also knows he's in a comic and thinks that he isn't meant to be in that strip.
 * One strip has Thaddeus and Bob in the dark, and the former points out that the reason his and Bob's eyes are visible is so the viewers can tell where the characters are in the dark, but then (along with Bob) berates a live-action author for being lazy and not drawing much.
 * Another strip that also has the characters talk to the author shows Thaddeus and Bob complaining that their "scripts" (which instruct them to say non sequiturs like "Farts" and "Something scientific") aren't funny.
 * In the Wizard of Oz parody, the not-very-bright bacterium says that the difference between "Oz" and "Awz" is "a copyright lawsuit".
 * In one strip, Thaddeus asks the creator why he's turning the park into a forest instead of continuing the comic. The creator replies, "I just like drawing trees."
 * In another strip, Thaddeus berates the creator for posting a comic despite not having any ideas.
 * One strip ends with Thaddeus yelling, "This comic doesn't exist!" to the author, as part of his spiel about how colours are an illusion, to which the author snidely responds, "Are you enjoying yourself?". Thaddeus then shows the author a goldfish, who dislikes the comic despite having four colour cones and being able to see more.
 * A strip depicts Thaddeus excited to see a giant hadron collider in Switzerland, but then he berates the author for being "lazy" due to not drawing it or his lower half. The author then searches for his eraser to rub Thaddeus out.