I remember I once found a DC superheroes campaign comic and was overjoyed... and it went hiatus after 5 or so pages.

Okay, I'm... getting confused. Is this a guest arc, or guest-collab arc? or are the players just... getting distracted in the middle of a session...?

I do not understand your confusion.

The players sung a song and are now talking about old campaigns they played in.

Yeah it's kinda confusing to take such a huge break in moving the plot forward, I don't know if this is some weird call for other people to join in making campaign comics or if it's just a huge kind of masturbatory reference about all kinds of different nerd culture/all about how great the campaigns these people have had before. I don't know how this fits in to the plot and it's taking too long.

aside from giving some context to how they know each other or what...
My guess is it will come back in the plot later, when we least expect it.
Also, it seem long because we're following the comic as it come and have to wait fo the update, but they've just been doing it for 3 pages or so.

HOW DEEP DOES THIS RABBIT HOLE GO?!

Are they implying that Wally West Flash wasn't already a comic book character in their universe?

Maybe he exist, but is'nt called Wally

In the universe the players inhabit, superhero comics do not exist. That's the premise of this entire flashback... maybe. But most of the other things we know and love (such as Batman: The Animated Series) do, albeit modified by the lack of these comics:

-Joe Shuster is known mostly for illustrating Nights of Horror.
-Without the success of Marvel and DC Comics, live-action adaptations of Japanese manga dominated Hollywood's blockbuster action scene.
-Nerdy guys still make YouTube videos of themselves debating geniuses vs gods. That hasn't changed.
-The use of yellow to indicate narration was popularized by webcomics.
-X-Men was licensed by Warner Bros for a short period before getting picked up by Disney.
-The major heroism-themed TV show that pervades all of western culture is Heroes, despite it never being as popular as Superfriends... for some reason.
-Luke has an idea for a screencap comic called Darths & Droids, but hasn't really found the time to make it.
-DragonTrainer exists and is currently writing a crossover arc in his screencap comic with D&D Aangvanced.

must have been one hell of a campaign.
Now that mean the kids of this world never got to experience the joy of watching the justice league cartoon every saturday morning...

So.... if Luke was Watchdogman, does that mean Cory was Saitama? Or was it DM who played him and Cory played Genos?

I HAVE SO MANY QUESTIONS!

Wait a minute.

D&D Aangvanced already said Shelby made one punch man in her very first campaign.

Does this mean Luke played in that game as well?!?

Luke as DCA Flash? Yeah I can see it. Honestly DCAU had the BEST interpretations of the various characters. All of them had depth and real moments of growth and awesome.