This is what happens when a comic's story literally transcends the capacity of the page to contain it (or at least, when the author thinks so).
In a Textplosion, the comic becomes an illustrated novel, or even a novel without any illustration at all. Note that this does NOT include comics which are crammed with word balloons or narration; that would be a Wall of Text. If the format is still recognizable as a comic (that is, you have most panels with drawings happening in them), as opposed to a glorified novel with a few pictures or even none, you have not witnessed a Textplosion.
Causes for the shift can be rather diverse, to include such things as the plot mushrooming out of control, the author deciding they can better express themselves in pure text, or simple artistic laziness.
This is not necessarily a bad thing, depending on the nature of the story and whether a Textplosion is intended as its own sort of plot device. However, a sudden or long-term shift from graphic art to Textplosion, regardless of quality or content, often results in losing large portions of readership — since, after all, they came to read a comic.
- Cerebus ran several dozen issues which were almost entirely text save for a few panels and pages done in the classic illustrative style.
- Thieves & Kings is about 50% comic and 50% illustrated text.
- The entire Warrior comic, by The Ultimate Warrior. Check out Spoony's review of it. There's enough text to make your eyes hurt.
- Burne Hogarth, who had done the Newspaper Comic version of Tarzan for many years, published a couple of Graphic Novels using text taken directly from the original Edgar Rice Burroughs novels. The art is gorgeous, especially in Jungle Tales of Tarzan.
- Strangers in Paradise did this from time to time, under the pretence that the reader was looking at pages from a SIP prose novel.
- An issue of Scion paid homage to Prince Valiant by being made in the same style. The art was laid out sideways, formatted like a Sunday newspaper strip, and the text was separate from the art, just like in Prince Valiant. An earlier, acclaimed issue of Scion was formatted like an illustrated novel, with blocks of text, sometimes integrated with the art.
- There's at least one scene in Bastard!! where the author just outright goes "I don't feel like drawing this, so let me describe what happened instead."
- Hunter × Hunter can get a bit silly about this occasionally. Because much of the fighting action revolves around characters overthinking about the moves and strategies of their foes, you can sometimes end up with whole pages dedicated to their thought processes alone.
- The writer of Erfworld started doing text updates to cover the gap between the strip's first and second artists. The updates were accompanied by a single panel of fan art and generally followed the comic's main story. When the second artist started to have personal issues, the text updates returned, and were eventually announced as becoming a permanent part of the strip. Between the second and third artists, text updates returned full time to flesh out the backstories of some secondary characters. With a new artists on board, the comic now alternates panels and text in the main storyline, and there are now weekly updates to text-only stories inspired by the strip's Kickstarter backers.
- Elf Life has vacillated between comic and novel styles over the years.
- Some Rogues of Clwyd-Rhan strips use wordless strips with text boxes rather than regular comic format.
- In God(tm) several textplosions are used to interrupt the story to explain such things as the Robotech Saga and a system of censorship.
- Keith Knight sometimes lets the text dominate over the art in his cartoons.
- Several instances of Subnormality go beyond Wall of Text and straight into this trope.
- Homestuck may count, as all dialogues are shown below the illustrations, and some are quite long.
- Goblins sometimes has filler in the form of a single panel depicting another one of the previous paladins who wielded the magic axe and a long description of how they got it.
- Alien Dice features a paragraph accompaniment below ever comic. Sometimes the text restates what just happened, and sometimes it tells a completely different story, which can lead to some confusion.
- Ctrl+Alt+Del switched into this for the "Winter-een-mas 2012/Game Games Bowl" story-arc. Tim Buckley has said that doing it in comic-form would have taken several months, long past the Winter-een-mas "season," and that he didn't want to do another long-term comic story arc so soon after the "Scott and Ted" arc. It...worked pretty well, actually.