Darths & Droids is about roleplayers playing a tabletop RPG following the basic plot of the Star Wars movies, but the notes on strip 50 have specifically stated that there is no Star Wars in the universe where they are. They then extrapolate on how that would impact things such as Mark Hamill's and Harrison Ford's careers, Spaceballs, the fate of sci-fi in media, and finally what the webcomic Darths & Droids would be parodying instead of Star Wars: Harry Potter.
On the other hand, once you get deep enough into the recursion, the outer layers could actually start reappearing, and the entire thing could come full circle. After all, there's no reason why Star Wars couldn't exist in a world where the characters are playing a home-brew RPG based on 300. In fact in the world where the Comic Irregulars are making a screencap comic based on Pirates of the Caribbean, it is stated that Keira Knightley is known primarily for her role in The Phantom Menace.
The final layer will be the first Futurama movie everyone starred in.
Star Wars already exists in the Sound of Music RP 'verse, if the titles are anything to go by (It's a von Trapp!).
Problem is, we're the outermost layer. What story are our roleplayers acting out?
It's also worth noting that in the universe where Jim, Ben, Pete, Annie, Sally and Corey are playing a given game, the Comics Irregulars are still making a screencap comic about a fictional roleplaying group with their names and personalities...
Ashe Rhyder's Roommates fancomic completely reverses this trope. Both the movies/books and the characters from them exist. The characters often watch their own movies, mention their actors, or refer fan service.
Jareth: "Wait. Javert... When the hell did you get so bloody tall?!" Javert: "As it turns out, Quast is tall. Bet you wish Bowie wasn't so short."
ThisMenage A 3 Strip: the authors of the comic, as authors of their other comic selling merchandise for it.
An The Order of the Stick comic has a semi-canonical episode where Gary Gygax appears in the afterlife, meeting with Roy. Since this is a world in which Dungeons & Dragons and Gygax do not exist, but which is heavily based on D&D (a specific edition of it, no less) to the extent that characters talk about experience points and +1 swords, this is... confusing.
Likewise, when Lord Shojo as a spirit adviser tell Belkar to "play the game" (he means for Belkar to conceal his sociopathic tendencies in order to fit into and better take advantage of society) Belkar is confused since he points out their world is not a game like D&D but a world that generally conforms to the rules of the game of D&D, to which Shojo replies "not this game!" indicating some knowledge of the game despite it not existing.
Spinnerette explains that superhero comics in this verse are actually merchandising deals with actual superheroes, either directly or Very Loosely Based on a True Story. This leads to Spinnerette making her original costume out of sewn-together Venom costumes, and even having to change it because she got a cease-and-desist from Marvel for infringing on Spiderwoman.